ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

Digitale Medien

Complexes of 2,2′,2″-Nitrilotriphenol. Part 1. A Study of Bimolecular Nucleophilic Substitution at the Boron Atom (1987)

Müller, Edgar ; Bürgi, Hans-Beat

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 499-510

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The tetradentate ligand 2,2′,2″-nitrilotriphenol forms a boron complex III with an intramolecular, transannular N→B dative bond of 1.68 Å in a strained tricyclo[3.3.3.0]undecane chelating system. The complex reacts with nitrogen bases L, such as pyridine, quinuclidine and others, to form complexes III-L, in which the intramolecular B-N bond is replaced by one between B and the external nucleophile. In solution, this displacement reaction is reversible. It was studied by temperature-dependent NMR spectroscopy. The resulting reaction and activation parameters suggest that the reaction is a bimolecular nucleophilic substitution (SN2).

Zusätzliches Material: 7 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700303

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

2

Digitale Medien

Complexes of 2,2′,2″-Nitrilotriphenol. Part 3. Crystal and Molecular Structures of Three Aluminium Complexes (1987)

Müller, Edgar ; Bürgi, Hans-Beat

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 520-533

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Crystal and molecular structures of three Al(III) complexes of the tripod ligand 2,2′,2″-nitrilotriphenolate (I) are presented. They all show 5-coordinate Al in approximately trigonal bipyramidal geometry, with an external nucleophile X occupying the second axial position. X is OH- in[Al(I)(OH)]-[Hquin]+ (quin = quinuclidine), N in [Al(I)(py)] (py = pyridine), and one of the O-atoms of a second molecule in the dimeric [(Al(I))2]. Correlated variations in the axial bond lengths of the trigonal bipyramid are observed: [(Al(I))2]: Al-Nint. = 2.094 Å, Al-Oext. = 1.850 Å; [Al(I)(py)]: Al-Nint. = 2.153 Å, Al-Next., = 1.992 Å; [Al(I)(OH)]-: Al-Nint. = 2.278 Å, Al-Oext. = 1.765 Å. They are interpreted in terms of a dissociative reaction path at the Al(III) centre.

Zusätzliches Material: 6 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700305

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

3

Digitale Medien

Molluscicidal Saponins from Swartzia madagascariensis DESVAUX (1987)

Borel, Christian ; Hostettmann, Kurt

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 570-576

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The phytochemical investigation of the dried fruits of Swartzia madagascariensis (Leguminosae) afforded the five triterpenoid saponins 1-5. They were shown to be glucuronides of oleanolic acid and of gypsogenin by chemical and spectral means (FAB-MS, 13C-NMR, GC/MS). One of the isolated compounds, identified as 3-O-[O-α-L-rhamnopyranosyl-(1→3)-(β-D-glucopyranosyluronic acid)]oleanolic acid, was responsible for the high molluscicidal activity of Swartzia madagascariensis fruits against the schistosomiasis-transmitting snails Biomphalaria glabrata and Bulinus globosus.

Zusätzliches Material: 1 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700309

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

4

Digitale Medien

The Hydrolysis of Ethyl 1-Methyl-2,4-cyclopentadiene-1-carboxylate by Nonenzymatic and Enzymatic Methods. Carbon-Carbon vs. Carbon-Oxygen Bond Cleavage (1987)

Burger, Ulrich ; Erne-Zellweger, Dominique ; Mayerl, Christa

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 587-592

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The title ester 5 is shown to undergo C-C bond cleavage under the conditions of basic ester hydrolysis (KOH/EtOH) with formation of potassium ethyl carbonate (6) and the tautomeric methylcyclopentadienes 7 and 8. In contrast, porcine liver esterase (PLE, EC 3.1.1.1) cleanly hydrolyses 5 to give the isolable 1-methyl-2,4-cyclopentadiene-1-carboxylic acid (13). The latter undergoes thermal dimerization with conservation of the geminal-substitution pattern. The configuration of the Diels-Alder adduct 17 is ascertained by it photochemical transformation into bishomocubane dicarboxylic acid 12, easily distinguished by its C2 symmetry. Under the conditions of acid-catalyzed hydrolysis, dimerization of ester 5 and polymerization prevail, unless low acid concentration is used. The dimer 9 of 5 has one ester function that is reluctant to undergo basic hydrolysis.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700311

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

5

Digitale Medien

Potassium Carboxylates by Direct Carbonylation of Potassium Alkoxides (1987)

Rautenstrauch, Valentin

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 593-599

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Reaction of the K+ alkoxide of linalool (1) in benzene with CO at 425-440 bar and 120-130° for 12-30 h gave the K+ salt of 2,6-dimethyl-2-vinyl-5-heptenoic acid (4a) in a ca. 25% yield based on ca. 65% converted alkoxide. Reaction of the [K+ ⊂ 18-crown-6] alkoxide of 1 with CO at 50-55 bar and 40° for 90-140 h gave a mixture containing mainly the [K+ ⊂ 18-c-6] salts of 4a (ca. 62%) and of the homogeranic acids 3a and 6a (together ca. 27% of the mixture) in a ca. 35% combined yield based on 50-60% converted alkoxide. The uncomplexed or complexed K+ alkoxide of (S)-1 gave, with ca. 85% net retention, the K+ salt of (S)-4a. Reaction of the [K+ ⊂ 18-c-6] alkoxide of geraniol (2) with CO at 50 bar and 40° for 65-70 h gave myrcene (10) and geranyl formate (11) in a ca. 40-50% yield each based on ca. 85% converted alkoxide. Reaction of the [K+ ⊂ 18-c-6] alkoxide of 3-pentyl-1,4-pentadien-3-ol (14) at 50 bar and r.t. for 70 h gave a mixture of the [K+ ⊂ 18-c-6] salts of 2-pentyl-2-vinyl-3-butenoic acid (15a) (67%) and the 4-pentyl-2,4-hexadienoic acids 18a and 19a (together 23% of the mixture) in a ca. 90% combined yield based on ca. 65% converted alkoxide.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700312

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

6

Digitale Medien

Synthesis and Copper(I) Complexes of a Series of 9- to 13-Membered N3 Macrocycles (1987)

Briellmann, Markus ; Kaderli, Susan ; Meyer, Charles J. ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 680-689

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Eight cyclic triamines with ring sizes between 9 and 13 were synthesized by the p-toluenesulfonate method. The open-chain triamines bis(2-aminoethyl)amine (dien) and bis(3-aminopropyl)amine (diprop) were used as starting materials. In some cases, the corresponding dimeric cyclic hexaamines have been isolated and characterized as major by-products. The complexation of Cu(I) by the triamines has been studied potentiometrically in CH3CN/H2O. All ligands L form ternary complexes [Cu(CH3CN)L]+. The corresponding association constants vary between 1011 and 107, decreasing with increasing ring size. In addition, complexes [Cu(CH3CN)yLH]2+, y = 1 or 2, are found as less important species with maximum concentrations of 7 to 50%.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700318

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

7

Digitale Medien

The Microstructure of Selective Palladium Hydrogenation Catalysts Supported on Calcium Carbonate and Modified by Lead (Lindlar Catalysts), Studied by Photoelectron Spectroscopy, Thermogravimetry, X-Ray Diffraction, and Electron MicroscopyThe following abbreviations and acronyms are used in the text: B. e. : Binding energy [eV], BET: Brunauer-Emmett-Teller (method of surface-area determination by physisorption of N2), AES: Auger electron spectroscopy, XPES: X-ray photoelectron spectroscopy, UPES: Ultraviolet photoelectron spectroscopy, ISS: Ionscattering spectroscopy, UHV: Ultrahigh vacuum (10-5 Pa), FTIR: Fourier-transform IR spectroscopy, TGA: Thermal gravimetric analysis, XRD: X-ray diffraction, XDA: Energy dispersive microanalysis, SEM: Scanning electron microscopy, TEM: Transmission electron microscopy, FWHM: Full width at half maximum. (1987)

Schlägl, Robert ; Noack, Klaus ; Zbinden, Heinz ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 627-679

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: A detailed analysis of the system Pd + Pb on CaCO3 is presented. This system known as Lindlar catalyst is used for selective hydrogenations of C≡C bonds to C=C bonds. It was found to consist of seven distinct chemical phases. Essential ingredients are solid solutions of hydrogen and oxygen in Pd. The latter phase enables the metal particles to be attached to the support via an orientational relationship calcite (113)∥Pd + O (111). The addition of Pb neither changes the micromorphology of the disk-shaped Pd particles nor does it modify the electronic structure of Pd as studied by chemisorption experiments. The addition of Pb seems to block certain active sites and, thus, to enhance the selectivity. The support was found to be a multi-domain mixture of calcite and aragonite with domain sites of several hundred Å. The free surface of the pore-free solid is covered by a calcium-hydroxide carbonate. This phase as well as several other Pb phases seem to represent only spectator materials. Verification of this as well as finding the correlation between structure and function of the various components requires a kinetic analysis which is outside the scope of this paper. It is demonstrated that a variety of analytical techniques is required to unravel the complex nature of such a ‘simple' catalyst’ as it is Pd on CaCO3.

Zusätzliches Material: 36 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700317

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

8

Digitale Medien

Verapliquinones: Novel Diprenylquinones from an Aplidium sp. (Ascidiacea) of Ile-Verte Waters, Brittany (1987)

Guella, Graziano ; Mancini, Ines ; Pietra, Francesco

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 621-626

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: An Aplidium sp. (Ascidiacea), collected in French Atlantic waters near the Ile Verte, is shown to contain verapliquinone B (2) and verapliquinone D (6) as the first examples of linear diprenylquinones of the neryl type, besides their respective isomers 1 and 5 of the geranyl type.

Zusätzliches Material: 2 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700316

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

9

Digitale Medien

Fe(II)-Induced Fragmentation Reaction of γ-Hydroperoxy-α,β-enones. Part 1. Synthesis of 13(14→8)-abeo-Steroids (1987)

Canonica†, Luigi ; Danieli, Bruno ; Lesma, Giordano ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 701-716

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Some steroidal analogues embodying the hitherto unknown 13(14→8)-abeo skeleton have been synthesized by Fe(II)-induced rearrangement (tandem β-fission/reductive alkylation) of 14α-hydroperoxy-7-en-6-ones. The configurational assignment was made by thorough analysis of NMR spectra; the structure of one of the products was unambiguously assessed by X-ray single-crystal analysis.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700320

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

10

Digitale Medien

Light-Induced, Thermal, and Acid-Catalyzed π-Skeletal Rearrangements of Five-Ring-Annelated HeptalenesPresented in part by H.-J.H. in a lecture at the ETH in Zürich, 1985. (1987)

Weber, Roland H. ; Brügger, Paul ; Jenny, Titus A. ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 742-759

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: It is shown that, upon irradiation in CDCl3 solution, 5,6,8,10-tetramethylheptalene-1,2-dicarboxylic anhydride (6) rearranges to its double-bond-shift (DBS) isomer 7 in an equilibrium reaction (Scheme 2). The isomer 7 is DBS stable at -50°. At ca. 30°, a thermal equilibrium with 97.8% of 6 and 2.2% of 7 is rapidly established. Similarly, the ‘ortho’-anhydrides 9 and 11 (Schemes 4 and 5) can be rearranged to their corresponding DBS isomers 12 and 13, respectively. Whereas 12 is DBS stable at 30° (at 100° in tetralin, 94.0% of 9 are in equilibrium with 6.0% of 12), the i-Pr-substituted isomer 13 is already at 30° in thermal equilibrium with 11 leading to 98.7% of 11 and 1.3% of 13. It is shown by rearrangement of diasteroisomeric ‘ortho’-anhydrides of known relative and absolute configuration (Scheme 6) that the DBS in such five-ring-annelated heptalenes occurs with retention of the configuration of the heptalene skeleton as already established for other heptalene compounds. It is found that the DBS process may also take place under acid catalysis (e.g. HCl/CH3OH), thus yielding 9 from 12 (Scheme 9). The ‘ortho’-anhydrides 21 and 23 (Scheme 10) which are isomeric with 9 and 11 (Scheme 3) undergo rapid DBS' already at room temperature. The thermal equilibrium 21⇄22 consists of 18% of 21 and 82% of 22 at 30° and that of 23⇄24 of 17% of 23 and 83% of 24 at -30°. From these equilibrium mixtures, the pure DBS isomer 22 can be obtained by crystallization. Again, these rapid DBS' occur with retention of configuration of the heptalene skeleton (Fig. 4).

Zusätzliches Material: 4 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700323

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

11

Digitale Medien

Synthese und NMR-Spektren von Nonafulven sowie Vergleich mit 10-PhenylnonafulvenHerrn Prof. Dr. Hans Nitschmann zum 80. Geburtstag gewidmet52. Mitt. über Fulvene, Fulvalene; 51. Mitt. [1]; Kurzmitt. [2]. (1987)

Furrer, Jürg ; Bönzli, Peter ; Frey, Alfred ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 862-880

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Synthesis and NMR Spectra of Nonafulvene and Comparison with 10-PhenylnonafulveneExperimental procedures for the reaction of cis,cis,cis,trans-cyclononatetraenide (ccct-CNT-; see 4) with bromomethyl acetate (1a, R = H, X = Br) to give (cyclononatetraenyl)methyl acetate (5a; 84% yield) as well as for the base-induced elimination of HOAc from 5a to give nonafulvene (6a; 44% yield) are described. Spectroscopic as well as chemical evidence for 6a and 6b is presented. An approximate high-field-NMR analysis of 6a and 6b has been completed. The results are in favour of a fast interconversion of the type 6A⇄6B (Scheme 4), and supported by the MNDO-optimised geometry of 6a. The first X-ray analysis of a cyclononatetraene (i.e. of 5b) has been accomplished: 5b is a polyolefinic molecule with largely alternating bond lengths and with a nine-membered ring deviating strongly from planarity.

Zusätzliches Material: 7 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700327

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

12

Digitale Medien

Field-Desorption Mass Spectra of Fern Phloroglucinols Containing Three to Six Ring ConstituentsDedicated to the late Prof. Peter Brown (12.IX.1938-15.III.1981), Dept. of Chemistry, Arizona State University, Tempe, Arizona 08521, U.S.A., Whose premature death was a great loss to his friends and collegues. The last letter which we received from him (November 15, 1980) contained the first FD mass spectra of five relatively large fern phloroglucinols which he had successfully analyzed. Two of these spectra, in which no thermal rearrangement and /or fragmentation was observed, are reproduced in this article (1987)

Richter, Wilhelm J. ; Raschdorf, F. ; v. Euw, Josef ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 881-893

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: It has been previously shown that the structural analysis of the title compounds by electron-impact ionization (EI)mass spectrometry is complicated by extensive, if not complete, thermal rottlerone-type rearrangement and/or fragmentation reactions. The use of a ‘softer’ ionization technique such as field desorption (FD) is, therefore, required in order that these compounds may be characterized in terms of their molecular size and composition. In this report, the FD mass spectra of typical representatives of this class of compounds are described along with the attempted suppression of undesirable thermal reactions by the optimization of the emitter temperatures.

Zusätzliches Material: 7 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700402

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

13

Digitale Medien

Structures and Electrical Properties of Some New Organic Conductors Derived from the Donor Molecule TMET (S,S,S,S,-Bis(dimethylethylenedithio) tetrathiafulvalene) (1987)

Karrer, Andreas ; Wallis, John D. ; Dunitz, Jack D. ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 942-953

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Crystal structures and electrical properties of radical-cation salts of the chiral organic donor TMET (S,S,S,S,-bis-(dimethylethylenedithio)tetrathiafulvalene) are described. Two structural types, 2:1 with octahedral anions Pf-6, AsF-6, SbF-6, I-3 (incommensurate), and 3:2 with tetrahedral anions BF-4, CIO-4, ReO-4 are observed. Resistivity measurements between 2 and 298 K indicate that the 3:2 types are organic metals, while the other compounds are semiconductors. (TMET)3(CIO4)2 is metallic down to about 120 K at ambient pressure and remains metallic down to 2 K at 8 kbar.

Zusätzliches Material: 10 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700405

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

14

Digitale Medien

Bildung tricyclischer Thietan-Derivate durch intramolekulare(2+2)-Cycloaddition (1987)

Wipf, Peter ; Heimgartner, Heinz

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 992-994

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Formation of Thietane Derivatives via Intramolecular (2+2) CycloadditionOn irradiation, the two 4-vinyl-1,3-thiazole-5(4H)-thiones 1a, b, synthesized from thiobenzoic acid and the corresponding 3-amino-2H-azirines 2a,b, undergo an intramolecular (2+2)-cycloaddition reaction of the C=S and C=C bonds to give the tricyclic thietane derivatives 3a,b.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700409

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

15

Digitale Medien

Photochemical Synthesis of 2-Alkylidene-1,3-cyclocalkanediones. Preliminary Communication (1987)

Hobel, Klaus ; Margaretha, Paul

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 995-996

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Photolysis (λ = 254 nm) of 4-(tert-butyl)-4,6,7,8-tetrahydro-7,7-dimethy-2H-1-benzopyran-2,5(3H)-dione (3a) in t-BuOH affords 2-(2,2-dimethylpropylidene)-5,5-dimethyl-1,3-cyclohexanedione (1a) in 80% yield via homolysis of the lactone O—CO bond and subsequent ketene elimination.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700410

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

16

Digitale Medien

Some Cyclic Oligopeptide with S2n Symmetry (1987)

Tomasic, Lera ; Lorenzi, Gian Paolo

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1012-1016

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Some cyclic oligopeptides formed by an equal number of alternating D- and L-amino-acid residues have been synthesized by using the hydrochloride of the open-chain peptide acid as precursor and the mixed-anhydride condensation method. The cyclic oligopeptides (tetra-, hexa-, and octavaline, hexaleucine, and hexaphenylalanine) form very stable H-bonded structures (IR-amide band at 3270-3290 cm-1) which are insoluble in common organic solvents. In CF3COOH/CDCI3 (25°), they yield 1H-NMR spectra snowing the expected equivalency of the various amino-acid residues.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700413

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

17

Digitale Medien

Strukturaufklärung ungewöhnlicher Umlagerungsprodukte von S-(1-Alkenyl)sulfoximiden mit Hilfe der Stossaktivierungsmassenspektrometrie (CAD-MS) (1987)

Veith, Hans-Jürgen ; Gais, Hans-Joachim ; Erdelmeier, Irene

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1041-1049

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Structure Determination of Unusual Rearrangement Products of S-(1-Alkenyl)sulfoximides by Collisionally Activated Dissoication Mass Spectrometry (CAD-MS)The Molecular ions of s-(l-alkenyl)--N-(p-tolyl)sulfoximides 1 are transformed into the N(phenylsufenyl)sulfonamides 3+ by a 1,2-migration of the alkenyle group to the O-atom of the sulfoximide function followed by a 2,3-sigmatropic rearrangement. The structure of the production e has been unambiguouslydetermined by the CAD method, showing the identity of the ion e (m/z368) obtained from 1a and from 4a.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700416

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

18

Digitale Medien

Reaktionen von 1,2-Bis(trimethylsilyl)iminen mit Selen-und Tellur-halogeniden (1987)

Neidlein, Richard ; Knecht, Dagmar

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1076-1078

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Reactions of 1,2-Bis(trimethylsilyl)imines with Selenium and Tellurium HalogenidesThe reactions of benzil-bis(trimethylsily)imine and phenanthrene-9,10-bis(trimethylsilyl)imine with SeOCl2, SeCl4 and TeCl4 are described.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700420

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

19

Digitale Medien

Remote Tricarbonyl(diene)iron Substituent Effect on Ester Heterolysis. The Solvolyses of 5,6,7,8-Tetramethylidenebicyclo[2.2.2]oct-2-yl Methanesulfonate and of its Tricarbonyliron Mono- and Dinuclear ComplexesPart of Ph.D. thesis of J.-C. Zwick, Ecole Polytechnique Fédérale de Lausanne, 1987. Part of this work has been presented at the Fall Meeting of the Swiss Chemical Society in Bern, Oct. 10, 1986. (1987)

Zwick, Jean-Christophe ; Gabioud, Rapny ; Vogel, Pierre

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1079-1094

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Buffered acetolyses and hydrolyses of 5,6,7,8-tetramethylidenbicyclo[2.2.2]oct-2-yl methanesulfonate (17), of its ‘syn-endo’ (18), ‘syn-exo’ (19), ‘anti-endo’ (20), ‘anti-exo’ (21) tricarbonyliron complexes and of its ‘anti-exo,syn-endo’ (22) and ‘anti-endo,syn-exo’ (23) bis(tricarbonyliron) dinuclear complexes have been investigated (product analysis and kinetics). In contract with the solvolyses of the uncomplexed mesylate 17, the solvolyses of the complexed esters can be highly chemo- and stereoselective. The nature of the products (non-rearranged bicyclo[2.2.2]oct-2yl vs. rearranged bicyclo[3.2.1]oct-2-yl derivatives) depends on the relative configuration of the tricarbonyl(diene)iron moieties and on the medium. The rates of solvolyses of 17 are only slightly affected by complexation of one or both s-cis-butadiene units with Fe(CO)3 groups, except in the cases where the diene moiety ‘anti’ with respect to the mesylate is complexed onto its ‘endo’ face (20,23). In these cases, significant rate-retardation effects are observed, consistent with the inductive effect of the Fe(CO)3 substituent. Such retardation effects are overwhelmed by competing accelerating homoallylic participation by uncoordinated ‘anti’ -diene moieties (18,19) or, as in the case of the ‘anti-exo’-Fe(CO)3 complexes 21 and 22, by possible direct metal participation to the ionization process.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700421

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

20

Digitale Medien

Synthetic Models of the Active Site of Cytochrome P-450. 1st Communication. The Synthesis of a Doubly-Bridged Iron(II)-Porphyrin Carrying a Tightly Bound Thiolate LigandPresented in part at the ‘Gordon Research Conference’ on the ‘Chemistry and Biology of Pyrroles’, New Hampshire, 27.7.-1.8.86 (W.-D.W.), and at the ‘Swiss Chemical Society’ meeting, Bern, 10.10.86 (B.S.). (1987)

Stäubli, Beat ; Fretz, Heinz ; Piantini, Umberto ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1173-1193

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The doubly-bridged iron(II)-tetraphenylporphyrin derivative 6, carrying a sterically fixed S- ligand in the ‘proximal’ position and the substrate at the ‘distal’ site, was synthesised as an enzyme model for cytochrome P-450. Compound 36, the CO complex of 6, displays a split Soret band (403 and 457 nm) similar to the native cytochrome P-450.

Zusätzliches Material: 7 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700425

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

21

Digitale Medien

Stereoselektive Alkylierung an C(α) von Serin, Glycerinsäure, Threonin und Weinsäure über heterocyclische Enolate mit exocyclischer DoppelbindungZughörige Kurzmitteilungen: [1] (Weinsäre) [2] (Threonin) [3] (Serin) [4] (Glycerinsäure).Siehe auch die Diskussionen in den vor kurzem erschienenen Übersichtsartikeln [5][6]. (1987)

Seebach, Dieter ; Aebi, Johannes D. ; Gander-Coquoz, Marlyse ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1194-1216

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Steroselective Alkylation at C(α) of Serine, Clyceric Acid, Threonine, and Tartaric Acid Involving Heterocyclic Enolates with Evocyelic Double BondsThe chiral, non-racemic title acids are converted to methyl dioxolane-(cf. 13), oxazoline-(4) and oxazolidinecarboxylates (cf. 9). Deprotonation by Li(i-Pr) 2N at dry-ice temperature gives solutions of the lithium enolates A-D With exocyclic enolate double bonds. These are stable crough with respect to β-elimination (Scheme 1) to be alkylated with or without cosolvents such as HMPA or DMPU The products are formed in good to excellent yields and, with the exception of the tartrate-derived acetonlde (see Scheme 2), with diastereoselectivities above 90%. While the tartrate-and threonine-derived enolates (A and B, resp.) are chiral due to the second stereogenic center of the precursors, the serine- and glyceric-acid-derived enolates (Aand B, resp.) are chiral due to the second sterogenic center of the precursors, the serine-nd glyceric-acid-derived enolates are non-racemic due to a tert butyl-substituted (pivalaldehyde-derived) acetal center (C and D, resp.). The products of alkylation can be hydrolyzed to give α-branched tartaric acid (Scheme 2), allothreonine (Scheme 3), serine (Scheme 4), and glyceric-acid derivatives (Scheme 5) with quaternary stereogenic centers. The configurations of the products are determined by NOE-NMR measurements and by chemical correlation. These show that the dioxolane-derived enolates A and D are alkylated preferentially from that face of the ring which is already substituted (‘syn’-attack), while the dihydrooxazol-and oxazolidine-derived enolates B and C are alkylated from the opposite face (‘anti’-attack). The ‘syn’-attack is postulated to arise from strong folding of the heterocyclic ring due to electronic repulsion between the enolate π-system and non-bonding electron pairs on the heteroatoms (see Scheme 6).

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700426

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

22

Digitale Medien

Novel Synthesis of Agaritine, a 4-Hydrazinobenzyl-Alcohol Derivative Occurring in Agaricaceae (1987)

Datta, Subir ; Hoesch, Lienhard

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1261-1267

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The 4-hydrazinobenzyl alcohol (3 was prepared (58%)) by diiobutylaluminiumhydride reduction of methyl 4-hydrazinobenzoate (4), whereas LiA1H4 or LiBh4 reduction of4 proceeded further to yield (via intermediate 3) (4-tolyl)hydrazine (5). The alcohol 3 was stable under O2-free conditions and exhibited no tendency to eliminate H2O, neither thermally nor with H+ catalysis. Oxidation of 3 with SeO2 yielded 4-(hydroxymethyl)benzine-diazonium ion (8), identified by its azo coupling product 9 with 2-naphthol. Condensation of 3 with 1-benzyl 5-Hydrogen N-(benzyloxycarbonyl)-L-glutamate (10) in presence of dicyclohexylcarbodiimide afforded 81% of N2-(benzyloxycarbonyl)-L- glutamic acid 1-(benzyl-ester) 5-{2-[4-(hydroxymethyl)phenyl]hydrazide} (11) which upon controlled hydrogenolysis (quinoline-sulfur-poisoned Pd/C catalyst) gave 82% of L-Glutamic acid 5-{2-[4-(hydroxymethyl)phenyl] hydrazide} (1), i. e. agaritine, a metabolite of Agaricus bisporus. Without poisoning of the catalyst, hydrogenolysis of (11) yielded L-glutamic acid 5-[2-(4-tolyl)hydrazide] (12).

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700505

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

23

Digitale Medien

The Solid and Solution Conformations of (±)-Corycavine (1987)

Kamigauchi, Miyoko ; Iwasa, Kinuko ; Takao, Narao ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1482-1486

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The crystal structure of corycavine, a protopine-type alkaloid, has been determined by X-ray analysis. A conformational feature observed is the existence of a strong electrostade interaction between the N- and C-atom at a distance of 2.618 Å. Such an interaction stabilizes the 10-membered ring conformation of the structure. Analyses of NMR spectra indicate that corycavine has the same conformation in solution as in the crystal state.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700605

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

24

Digitale Medien

Dimethylformamide-Exchange Mechanism on Some First-Row Divalent Transition-Metal IonsPart 33 of the series ‘High-Pressur NMR Study’. Part 32: [1].Taken in part from the diploma work of C. Cossy, Université de Lausanne, 1983.This work was presented in part at the 24th International Conference on Coordination Chemistry, Athens, Greece, August 1986. (1987)

Cossy, Cédric ; Helm, Lothar ; Merbach, André E.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1516-1525

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The effect of temperature on the dimethylformamide exchange on Mn(DMF)2+6 and Fe(DMF)2+6 has been studied by 13C- and 17O-NMR, respectively, yielding the following kinetic parameters: k298 equals; (2.2±0.2). 106 S-1, ΔH≠ = 34.6 ± 1.3 kJ mol-1, ΔS≠ = -7.4 ± 4.8 J K-1mol-1 for Mn2+ and K298 = (9.7 ± 0.2).105 S-1, Delta;H≠ = 43.0 ± 0.9 kJ mol-1, ΔS≠ = + 13.8 ± 2.8 J K-1mol-1 for Fe2+. The volumes of activation, ΔV≠ in cm3mol-1, derived from high-pressure NMR on these metal ions, together with the previously published activation volumes for Co2+ and Ni2+ (+2.4 ± 0.2 (Mn2+), +8.5 ± 0.4 (Fe2+) +9.2 ± 0.3 (Co2+), + 9.1 ± 0.3 (Ni2+)) give evidence for a dissociative activation mode for DMF exchange on these high-spin first-row transition-metal divalent ions. The small positive ΔV≠ value observed for DMF exchange on Mn2+ seems to indicate that a mechanistic changeover also occurs along the series, (probably from Id to D), as for the other solvents previously studied (Ia to Id, for H2O, MeOH, MeCN). This changeover is shifted to the earlier elements of the series, due to more pronounced steric crowding for dimethylformamide hexasolvates.

Zusätzliches Material: 5 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700608

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

25

Digitale Medien

Two New Antifungal Naphthoxirene Derivatives and their Glucosides from Sesamum angolense WELW (1987)

Potterat, Olivier ; Stoeckli-Evans, Helen ; Msonthi, Jerome D. ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1551-1557

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Two novel naphthoxirene derivatives 1 and 2 their glucosides 3 and 4 have been isolated from the root bark of Sesamum angolense Welw. (Pedaliaceae) by preparative liquid chromatography. The structure of 1 was established by X-ray diffraction analysis. The identities of the other naphthcxirenes were deduced by spectroscopic (IR, UV, 1H-NMR, 13C-NMR, EI-MS, DCI-MS) and chemical methods (oxidation, acid and enzymatic hydrolysis). Compounds 1-3 exhibited antifungal activity. Naphthoxirene 1 was, in addition, cytotoxic to human colon carcinoma cells.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700613

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

26

Digitale Medien

On Negative Birefringence in Water-in-Oil Microemulsions (1987)

Hilfiker, Rolf ; Eicke, Hans-Friedrich ; Hammerich, Holger

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1531-1536

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The occurrence of a negative birefringence in water-in-oil (W/O) microemulsions has been substantiated and analyzed. The analysis is based on the well-established aqueous nanodroplet model of W/O microemulsions. In the particularly investigated water/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/aliphatic oil systems, the AOT monolayer exhibits a negative induced intrinsic birefringence, which is brought about by the pronounced polarizability of the alkyl moiety of the AOT molecule approximately perpendicular to the direction of its permanent dipolement.

Zusätzliches Material: 4 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700610

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

27

Digitale Medien

Erratum (1987)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 2246-2246

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700829

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

28

Digitale Medien

Mitteilungen - Communications (1987)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 2305-2306

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700830

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

29

Digitale Medien

Herstellung und Charakterisierung in Membranen von Ionophoren mit Selektivität fü Natrium-Ionen (1987)

Bongardt, Frank ; Vögtle, Fritz ; Wegmann, Dorothée ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 153-157

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Preparation of Neutral Sodium-Selective Ionophores and their Characterization in Membrane ElectrodesDifferent ionopbores based on N,N′-dibenzyl-N,N′-diphenyl-1,2-phenylenedioxydiacetamide (1) have been prepared by substitution of the aromatic ring carrying the ether O-atoms. Substituents of widely different electronegativity (CH3, CH3O, CHO, CN NO2, Br) do not relevantly influence the ion selectivity.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700119

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

30

Digitale Medien

Complexes of 3,3′-Oxybis[(diphenylphosphino)methylbenzene] with Ni(II), Pd(II), Pt(II), Rh(I), and Ag(I). How Important is Backbone Rigidity in the Formation of trans-Spanning Bidenatate Chelates?? (1987)

Marty, Werner ; Kapoor, Pramesh N. ; Bürgi, Hans-Beat ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 158-170

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The bidentate diphosphine ligand, 3,3′-oxybis[(dipenylphosphino)methylbenzene] (1) forms monomeric, trans-square-planar complexes MX2(1) (M = Ni, Pd, Pt; X = Cl-, Br- I-, and, in part, N3-, NCS-, CN-, NO3-) as well as Pt(H)Cl(1), Pt(H)Br(1), and RhCl(CO)(1). Polymeric species have been observed with substitutionally inert metal centres: trans-[PtCl2(1)]2 and cis-[PtCl2(1)]n (mean value of n ≈ 4-5) 31P-NMR, and selected IR and UV/VIS parameters are reported. Ligand 1 shows a marked preference for trans-spanning and monomeric chelate formation, despite its various degrees of freedom of internal rotation in the lignad backbone. The readily available ligand 1 as well as analogues with other donor atoms, therefore, appear useful in most potential applications of trans-spanning chelate ligands. The crystal structure of AgCl(1)·0.5 (CH3)2C=O·0.39 C6H12 (space group C2/c,a = 21.02 Å, b = 14.57 Å, c = 24.79 Å, β = 99.77°, V = 7531.4 Å3, Z = 8) confirms the presence of three-coordinate Ag(I), with a coordination intermediate between a trigonal-planar and a T-shaped geometry (P-Ag-P = 145.61(8)°).

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700120

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

31

Digitale Medien

Aza-2-dienes-1,3. Partie 5. Préparation de N-aminoimidazoles, 3H-pyrroles, triazolo[1,2,4][1,5-a]pyrazines et imidazo[1,2-a]pyrazines (1987)

Legroux, Didier ; Schoeni, Jean-Paul ; Pont, Christiane ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 187-195

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: 2-Aza-1,3-dienes. Access to N-Aminoimidazoles, 3H-Pyrroles, [1,2,4]Triazolo[1,5-a]pyrazines, or Imidazo[1,2-a]pyrazinesNucleophilic attack of 5-(dialkylamino)-2-aza-1,3-diene-1,1-dicarbonitriles (or their 1-methoxycarbonyl analogous) by hydrazines or hydrazdes gives substituted N-aminoimidazoles, [1,2,4]triazolo-[1,5-a]pyrazines, or α-dihydrazino derivatives. With α-amino esters (or analogous), imidazo[1,2-a]pyrazines are produced. Addtion of cyanide anions occurs also with formation of substituted 3H-pyrroles. Structures and rationalisation of this nucleophilic attack are discussed.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700123

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

32

Digitale Medien

Syntheses of Tetrahydrolipstatin and Absolute Configuration of Tetrahydrolipstatin and Lipstatin (1987)

Barbier, Pierre ; Schneider, Fernand

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 196-202

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Lipstatin (1), a natural product, and tetrahydrolipstatin (2) are pancreatic lipase inhibitors. Non-stereoselective and partially stereoselective syntheses of 2 are used to establish the absolute configuration of tetrahydrolipstatin and lipstatin.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700124

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

33

Digitale Medien

Ring-Open Analogues of Adenine Nucleoside. Aminoacyl Derivatives of Cyclo- and Acyclo-Nucleosides (1987)

Hakimelahi, Gholam H. ; Zarrinehzad, Morteza ; Jarrahpour, Ali A. ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 219-231

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The synthesis of acyclic analogues of ribo- and deoxyribonucleosides is described. These compounds (Table 3) are both poor substrates and poor inhibitors of adenosine deaminase. The synthesis of dinucleotides from these analogues is also described, and the activity along with the inhibitory properties of some of them are studied against deaminase enzyme. These nucleotides are resistant to degradation by phosphodiesterases. HCl impregnated on silica gel is an excellent reagent for the preparation of the chloromethyl ether precursors of acyclo-nucleosides. A general and rapid procedure is developed for the preparation and isolation of the 5′-aminoacyl derivatives of robo- and arabinonucleosides. Quinoline has a marked effect on aminoacylations without racemization. Compounds 35a, b possess remarkable antiviral effects in vitro. A procedure is also developed for the conversion of acyclo-ribonucliosides 13e, f to acyclo-deoxyribonucleosides 11e, f.

Zusätzliches Material: 4 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700127

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

34

Digitale Medien

Functionalisation of saturated hydrocarbons. Part 9Part 8:[1].. Oxidation of patchouli alcohol by the ‘gif system’: Isolation and organoleptic properties of three new ketonic derivativesDedicated to Prof. Vlado Prelog on the occasion of his 80th birthday (1987)

Barton, Derek H. R. ; Belœil, Jean-Claude ; Billion, Annick ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 273-280

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Oxidation of patchouli alcohol (1) using the ‘Gif system’ afforded as major isolated products three new ketonic derivatives 16-18. The structures of these compounds were established by spectral techniques including 2D-NMR. Ketones 16-18 display interesting organoleptic properties.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700202

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

35

Digitale Medien

Synthese von ω-(5-Oxo-1-cyclopentenyl)alkansäure-methylestern aus 2-Nitrocycloalkanonen (1987)

Stach, Hans ; Hesse, Manfred

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 315-320

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Synthesis of Methyl ω-(5-Oxo-1-cyclopentenyl)alkanoates Starting from 2-NitrocycloalkanonesA convenient synthesis of methyl ω-(5-oxo-1-cyclopentenyl)alkanoates 1 is described. 2-Nitrocycloalkanones 2 are converted to 2-(3,3-dimethoxypropy1)-2-nitrocycloalkanones 4. Treatment of 4 with MeOH/MeONa led to the ring-opened nitronates 5 which underwent a Nef reaction to form the corresponding oxo derivatives 6. Partial hydrolysis of followed by base-catalyzed aldol reaction gave the desired products in high yields.

Zusätzliches Material: 2 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700207

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

36

Digitale Medien

Cyclobut-2-enones from Alkynes via Dichlorocyclobut-2-enonesIn part taken from the Ph.D. thesis of A.A.A., University of Zürich, 1986. (1987)

Ammann, Adrian A. ; Rey, Max ; Dreiding, André S.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 321-328

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The [2 + 2]-cycloaddition of dichloroketene (prepared in situ from CCl3COCl and Zn(Cu)) with three alkynes 1a-c to form 2,3-dimethyl-(2a), 2,3-diethyl-(2b) and 3-butyl-4,4-dichlorocyclobut-2-enone (2c) proceeds rapidly in the absence of POCl3. The primary products 2a-c rearrange in situ to the 2,4-dichlorocyclobut-2-enones 3a-c under the influence of ZnCL2 produced during the reaction. ZnCl2 converts both 2a and 3a into a 4:6 equilibrium mixture of the two; this isomerization does not occur with LiCl. The Cl-atoms of both 2a, b and 3a, band of 2c may reductively be removed with Zn(Cu) in AcOH/pyridine to afford the alkylcyclobutenones 4a-c. Without pyridine, this reduction gives ca. 1:1 mixtures of the double-bond isomers 4 and 5 in low yields. The cyclobutenones 2c and 4c may be deuterated by CD3COOD in the presence of pyridine. D-Atom is introduced into 2c at C(4) and at C(γ), and into 4c at C(2) and C(4). A mechanism for this deuteration is considered, which does not involve a cyclobutadienolate 7, but rather a cyclobutenolate of type 8. The reductions of 2 and 3 to 4 might also pass through the same type of intermediate 8.

Zusätzliches Material: 1 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700208

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

37

Digitale Medien

3-(Dimethylamino)-2,2-dimethyl-2H-azirin als α-Aminoisobuttersäure(Aib)-Äquivalent: Cyclische Depsipeptide durch direkte Amid-CyclisierungVorläufige Mitteilung s. [1]; vgl. auch [2]. (1987)

Obrecht, Daniel ; Heimgartner, Heinz

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 329-338

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: 3-(Dimethylamino)-2,2-dimethyl-2H,-azirine as an α-Aminoisobutyric-Acid (Aib) Equivalent: Cyclic Depsipeptides via Direct Amid CyclizationIn MeCN at room temperature, 3-(dimethylamino)-2,2-dimethyl-2H-azirine (1) and α-hydroxycarboxylic acids react to give diamides of type 8 (Scheme 3). Selective cleavage of the terminal N,N-dimethylcarboxamide group in MeCN/H2O leads to the corresponding carboxylic acids 13 (Scheme 4). In toluene/PhSH, phenyl thioesters of type 11 are formed (see also Scheme 5). Starting with diamides 8, the formation of morpholin-2,5- diones 10 has been achieved either by direct amide cyclization via intermediate 1,3-oxazol-5(4H)-ones 9 or via base-catalyzed cyclization of the phenyl thioesters 11 (Scheme 3). Reaction of carboxylic acids with 1, followed by selective amide hydrolysis, has been used for the construction of peptides from α-hydroxy carboxylic acids and repetitive α-aminoisobutyric-acid (Aib) units (Scheme 4). Cyclization of 14a, 17a, and 20a with HCI in toluene at 100° gave the 9-, 12-, and 15-membered cyclic depsipeptides 15, 18, and 21, respectively.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700209

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

38

Digitale Medien

Synthese von 2-Hydeoxy-3-methyl-2-hexen-4-olid (1987)

Stach, Hans ; Huggenberg, Walter ; Hesse, Manfred

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 369-374

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Synthesis of 2-Hydroxy-3-methyl-2-hexen-4-olidThe title compound 13a, a substance used in food-flavoring, was synthesized in 89% overall yield, starting from methyl 2-hydeoxy-3-butenoate (3a). The key step in this transformation is the isomerization of the C=C bond in 3a which yielded methyl 2-oxobutanoate as an intermediate. The latter underwent a self-condensation yielding 2-hydroxy-4-(methoxycarbonyl)-3-methyl-2-hexen-4-olid (11a), which, after hydrolysis and decarboxylation, gave 13a. In addition, the syntheses of five other compounds related to 13a are reported.

Zusätzliches Material: 1 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700214

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

39

Digitale Medien

Triaziridine 7. Mitteilung6. Mitteilung: [1].. Stabile pyramidale Konfigurationen an den Stickstoff-Atomen von Dialkyl-und Trialkyl-triaziridinen (1987)

Hilpert, Hans ; Hoesch, Lienhard ; Dreiding, André S.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 381-389

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Stable Pyramidal configurations at the Nitrogen Atoms of Dialkyl-and Trialkyl-triaziridinesStereochemical features of the recently synthesized nine samples of di- and trialkyl-triaziridines, namely the 1,3-cyclopentylen-(series a) and the two stereoisomers of the diisopropyl derivatives (series b and c), containing as the third substituent an H-atom (2), a CH3 group (3)or a CH2OH group (4), were elaborated on the basis of the 1H-, 13C-, and 15N-NMR spectra. The three N-atoms of the saturated N3-homocycle were found to be stable to pyramidal inversion in all cases. According to their NMR spectra, 2-4 of the series a and b possess twofold symmetry (Cs), while 2-4 of series c are asymmetric. Thus, series c has the trans-configuration at N(2)/N(3) and, consequently, the cis-configuration at N(1)/N(2), while series a and b have the cis-configuration at N(2)/N(3) and -since the all-cis-arrangement is excluded-the trans-configuration at N(1)/N(2). The asymmetry of the trans-configurated 2c turned into twofold symmetry (C2), when a little CF3COOH was added. The 1H- and 13C-NMR data of series b and c of our alkyl-triaziridines exhibit a shielding effect, according to which there are two types of i-Pr groups, i-Pr(a) and i-Pr(b). They differ in the NMR signals of the H- and the C-atoms of their CH groups: the H-atoms of i-Pr(a) are more deshielded by 0.75-1.111 ppm and its C-atoms are more shielded by 10.0-160.0 ppm as compared to the corresponding atoms of i-Pr(b). i-Pr(a) is cis (on the N3-homocycle) to a large substituent (such as i-Pr, Me, CH2OH) and to a lone pair, while i-Pr(b)is cis only to a small (H) or to no substituent and to one or two lone pairs. An analogous effect appears in the NMR signals of the CH3 and CH2OH groups at N(1) of 3 and 4 in the series b and c.

Zusätzliches Material: 2 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700216

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

40

Digitale Medien

Synthese eines Nickel(II)-B,C,D-hexadehydrocorrinats durch (A→D)-CyclisierungKurzmitteilung: [1].Professor Dr. Gerhard Quinkert zum 60. Geburtstag gewidmet (1987)

Montforts, Franz-Peter ; Bats, Jan W.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 402-411

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Synthesis of a Nickel(II) B,C,D-Hexadehydrocorrinate by (A→D)-Ring ClosureThe B,C,D-hexadehydrocorrin of type 10 fills a gap in the corrin family whose members can occur at different oxidation levels. We report here on the synthesis of a correspondingly protected secocorrin 23 and its convenient cyclization to 10

Zusätzliches Material: 3 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700219

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

41

Digitale Medien

Studies on the Biosynthesis of Tabtoxin (Wildfire Toxin). Origin of the Carbonyl C-Atom of the β-Lactam Moiety from the C1-Pool (1987)

Müller, Barbara ; Hädener, Alfons ; Tamm, Christoph

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 412-422

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Re-isolation of Pseudomonas tabaci strain NCPPB 2730 from its host, the tobacco plant, led to an activation of the bacteria in order to produce the β-lactam dipeptide tabtoxin (Wildfire toxin, 1). Incorporation of several 14C-labelled amino acids as well as L-[methyl-13C]methionine, L-[1,2-13C2]- and L-[3,4-13C2]aspartate, rac -[1,2-13C2]glycerol, and [1,2-13C2]acetate into isotabtoxion (2) demonstrated that the building blocks of tabtoxin (1) are L-threonine, L-aspartate, the Me group of L-methionine and a C2-unit derived from the C3-pool (Fig. 3). The Me group of L-methionine provides the carbonyl C-atom of the β-lactam moiety. These findings represent a novel pathway in β-lactam biosynthesis. Mechanistic aspects with respect to the β-lactam ring formation are discussed. A biradical 16 is proposed as an intermediate during the cyclization of a N-formyl-α-amino ketone 15.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700220

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

42

Digitale Medien

Mitteilungen - Communications (1987)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 488-491

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700229

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

43

Digitale Medien

On the Purported Structure of Cyclodeca[1,2,3-de: 6,7,8-d′e′]dinaphthalene (1987)

Gleiter, Rolf ; Schaaff, Hans Peter ; Rodewald, Hans ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 480-487

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The reaction of the bis(sulfonium salt)7 in a solution of Na2CO3 in H2O/EtOH yielded three main products 8-10. The spectroscopic data of 8 were identical to those which led Mithcell and Sondheimer to assign them to cyclodeca[1,2,3-de: 6,7,8-d′e′]dinaphthalene (3). Our investigations show, however, that the correct structural assignment leads to the structure of 7,7a-dihydrodibenzo[de,mn]naphthacene (8).

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700228

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

44

Digitale Medien

Masthead (1987)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987)

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700101

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

45

Digitale Medien

Mehrstufige Redoxsysteme. XLIX. MitteilungXLVIII. Mitteilung:[1]. Mit π-Systemen substituierte 1,3-Dimethylidencyclobutane: Synthese und Eigenschaften (1987)

Freund, Wolfgang ; Hünig, Siegfried

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 929-941

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Multistep Redox Systems. 1,3-Dimethylidenecyclobutanes Substituted by π-Syntheses and PropertiesAs potential redox systems 1,3-dimethylidenecyclobutanes are synthesized in which the ‘exo’-methylidene group participates in a cyclopentadienyl (typeC4)or cycloheptatrienyl (type A5) system. Benzo-annellated systems are also described. The formation of the C=C bond by the reaction of thioketones (3 and 31) with diazo compounds is extended to extended to 1,6,7,21, and 24, which so far had not been employed. In some cases, intermediate thiiranes can be isolated (e.g.4) which are smoothly transformed into the target compounds of types C4 and A5 by extrusion of sulfur. The new C=C bonds may be introduced stepwise, thereby allowing the synthesis of unsymmetrically substituted 1,3-dimethylidenecyclobutanes (e.g. 20 and 35). Reduction of by Na does not produce bicyclobutanes but compounds 43 and 44 with one dihydrofulvene unit.

Zusätzliches Material: 2 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700404

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

46

Digitale Medien

Verecynarmin A, a Novel Briarane Diterpenoid Isolated from Both the Mediterranean Nudibranch Molluse Armina maculata and its Prey, the Pennatulacean Octocoral Veretillum cynomorium (1987)

Guerriero, Antonio ; D'Ambrosio, Michele ; Pietra, Francesco

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 984-991

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The briarane diterpenoid verecynarmin A (=(-)).(8R,9S,11R,12aR,4Z,6Z)-11,12-epoxy-8,8a,9,10,12,12a,13-octahydro-1,5,8a,12-tetramethylbenzo[4,5]cyclodeca[1,2-b]furan-9-yl acetate; ((-)-1) is shown to be contained in both the Mediterranean nudibranch mollusc Armina maculata(RAFINESQUE) and its prey, the pennatulacean octocoral Veretillum cynomorium(PALLAS). The structure is mainly solved by 1D-NMR, 2D-NMR, and NOE studies of (-)-1. However, the relative configurations at the epoxide and angular methyl centres, as well as the preferred conformation, are established by shift-reagent and NOE studies of diol(-)-4 obtained by epoxide-ring opening of (-)-1 with LiA1H4. The absolute configuration is established via deacetylation of (-)01 followed by Horeau's esterification.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700408

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

47

Digitale Medien

Oxidationsreaktionen methyl-substituierter 2,1,3-Benzothiadiazole und 2,1,3-Benzoselenadiazole mit Selen-dioxid (1987)

Neidlein, Richard ; Knecht, Dagmar

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 997-1000

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Oxidation Reactions of Methyl Substituted 2,1,3-Benzothiadiazoles and 2,1,3-Benzoselenadiazoles with Selenium DioxideThe synthesis 5-8 by oxidation of 4-methyl-(1),5-methyl(2), 5,6-dimethyl-2,1,3-benzoselenadiazole (3), and 5,6-dimethyl-2,1,3-benzothiadiazole (4), respectively, with selenium dioxide as well as their spectroscopic properties are described.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700411

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

48

Digitale Medien

Steric Effects on Reaction Rates. Part IX. Force-Field Parameters for Bridgehead and Rigid Tertiary Carbenium Ions (1987)

Müller, Paul ; Mareda, Jiri

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1017-1024

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Molecular-mechanics calculations for strain of carbenium ions are tested using Bentley's unified reactivity scale for bridgehead solvolysis as reference. Excellent correlations are obtained for solvolytic bridgehead reactivity with the calculated steric-energy difference (ΔEst) between substrate (R—H or R—OH) and cation (R+). After adjustment of appropriate force-field parameters, the approach is successfully extended to the rigid, but planar cations derived from structures 15-20; however, the general set of parameters cannot be applied to highly strained systems such as the cation formed from 17. With all of the 18 sets of parameters tested, the 2-endo-norbornyl derivative 16, is adequately correlated, while the exo isomer 15 exhibits enhanced reactivity by a factor of ca. 102 to 103.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700414

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

49

Digitale Medien

Complexes of 2,2′,2″-Nirtilotriphenol. Part IV. Cage Compounds with Phosphorus(III) and Phosphorus(V) (1987)

Müller, Edgar ; Bürgi, Hans Beat

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1063-1069

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The ligand 2,2′,2″-nitrilotriphenol reacts with P(III) and P(V) compounds to form corresponding phosphorus complexes. Syntheses and NMR data of 2,2′,2″-nitrilotriphenyl phosphite (II), 2,2′,2″-nitrilotriphenyl phosphate (III) and of a hydrolysis product of II, 2,2′-[N-(2-hydroxyphenyl)imino]diphenly phosphonate (IV), are reported, as well as crystal structures of II and IV. Phosphite II shows a bicycloundecane framework; no NċPinteraction is present. The phosphonate IV shows two coordinated and one dangling phenol group; the N-atom does not interact with the P-atom. Strong acids protonate II as well as III to form cations: in these, NMR evidence indicates coordination of the N-atom to the P-atom.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700418

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

50

Digitale Medien

Octacarbonyldicoblat-Inauced (1,3) H Shits in 1-Methylallenecarboxylates and Allenic LactonesDedicated to Professor Dr. André S. Dreiding (1987)

Trifonov, Latchezar S. ; Orahovats, Alaxander S. ; Heimgartner, Heinz

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1070-1075

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The allenecarboxylates 1a,b and allenic lactones 4a,b undergo thermally induced (1,3) H Shifts in the presence of Co2(CO)8. The non-isolated 1,3-dienes 2a,b react further affording the Diels-Alder Adducts 3a,b Scheme 1 in high yields. These adducts were not formed in the case of the 2-vinybutenolides 5a,b. On irradiationin the presence of Co2(CO)8 or Mn2(Co)10, the studied allenes reacted in a different manner, yielding either cyclization products 7 and 8 (Scheme 3) or products 9 and 10, formed via H abstracton and solvent addition (Schemes 4 and 5).

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700419

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

51

Digitale Medien

Brominations of Cyclic Acetals from α-Amino Acids and α- or β-Hydroxy Acids with N-Bromosucinimide (1987)

Zimmermann, Jürg ; Seebach, Dieter

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1104-1114

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The preparation of novel electrophilic building blocks for the synthesis of enantiomerically pure compounds (EPC) is described. Thus, the 2-(tert-butyl)dioxolanones, -oxazolidinones, -imidazolidinones, and -dioxanones obtained by acetalization of pivalaldehyde with 2-hydroxy-, 3-hydroxy-, or 2-amino-carboxylic acids are treated with N-bromosuccinimide under typical radical-chain reaction conditions (azoisobuytyronitril/CCl4/reflux). Products of bromination in the α-position of the carbonyl group of the five-membered-ring acetals are isolated or identified (2, 5, and 8; Scheme 1). The dioxanones are converted to 2H, 4H-dioxinones under these conditions (12, 14, 15, 21, and 22; Schemes 2 and 3). The products can be converted to chiral derivatives of pyruvic acid (methylidene derivatives 3 and 6) or of 3-oxo-butanoic and -pentanoic acid (16 and 23). The mechanism of the brominations is interpreted. The conversion of serine to enactiomcrically pure dioxanones 26-28 (Scheme 4) is also discussed.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700423

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

52

Digitale Medien

Addendum (1987)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1229-1229

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700428

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

53

Digitale Medien

Mitteilungen - Communications (1987)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1230-1231

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700429

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

54

Digitale Medien

Enzyme-Catalyzed Hydrolysis of Some Functionalized Dimethyl MalonatesPresented at the meeting of the Swiss Chemical Society, Berne, October 10, 1986. (1987)

Luyten, Marcel ; Müller, Susanna ; Herzog, Beat ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1250-1254

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: A method is described for the preparation of (+)-(R)-methyl hydrogen 2-(tert-butoxymethyl)-2-methyl-malonate (5e) in synthetically useful amounts from readily available starting material.

Zusätzliches Material: 1 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700503

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

55

Digitale Medien

Diels-Alder-Reaktionen von 2,4-Bis{[(tert-butyl)dimethylsilyl]oxy}-3-aza-1,3-pentadien mit HeterodienophilenTeil der geplanten Dissertation von U. R. [1]. (1987)

Ried, Walter ; Reiher, Uwe ; Jan, W. Bats

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1255-1260

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Beschreibung / Inhaltsverzeichnis: Diels-Alder Reactions of 2,4-Bis{[(tert-Butyl)dimethylsilyl]oxy}-3-aza--1,3-pentadien with HeterodienophilesThe 2,4-bis{[(tert-butyl)dimethylsilyl]oxy}-3-aza-1,3-pentadien(2) reacts via the Diels-Alder adducts 3, 6a-c, and 8a, b, which cannot be isolated, giving the triazines 4, 7a-c, and the oxadiazines 9a, b. The hydrolysis of 4 in MeOH affords the N-acetyl-acetamid derivative 5. The formula of 9a is proven by an X-ray-structure analysis.

Notizen: No. Abstract.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700504

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

56

Digitale Medien

Zwei weitere Iridoid-glycoside und ein Monoterpen-glycosid aus Sambucus ebulus L. (Caprifloiaceae). 3. Mitteilung über die Inhaltsstoffe der Zwergholunderwurzel (1987)

Gross, Gian-Andrea ; Sticher, Otto ; Anklin, Clemens

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 91-101

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: New Iridoid Glycosides and a Monoterpene Glycoside from Sambucus ebulus L. (Caprifloiaceae)From the roots of Sambucus ebulus L., two novel valeriana-type ester iridoid glycosides, 6′-O-apiosylebuloside (1) and 7,7-O-dihydroebuloside (3), along with the open-chain monoterpene glycoside 5 were isolated. Their structure elucidation is based mainly on one- and two-dimensional NMR methods. 1H,1H-COSY experiments permitted complete assignment of signals arising from the disaccharide unit in 1. Biogenetically, 3 seems to represent the equivalent of loganin in the valeriana-type series of iridoid glycosides.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700111

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

57

Digitale Medien

Synthese von ‘D-Isothreonin’ und ‘L-Alloisothreonin’ aus L-Alanin (1987)

Wolf, Jean-Pierre ; Pfander, Hanspeter

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 116-120

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Synthesis of ‘D-Isothreonine’ and ‘L-Alloisothreonine’ Starting from L-AlanineStarting from L-alanine, ‘D-isothreonine’ ( = (2R, 3S)-3-amino-2-hydroxybutanoic acid) and ‘L-alloisothreonine’ ( = (2S, 3S)-3-amino-2-hydroxybutanoic acid) were synthesized.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700113

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

58

Digitale Medien

Oxidative Breaking of Long-Chain Acetylenic Enol Ethers of Glycerol of the Marine Sponges Raspailia pumila and of Model Compounds with Aerial Oxygen (1987)

Guella, Graziano ; Mancini, Ines ; Pietra, Francesco

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1400-1411

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The raspailynes (novel long-chain enol ethers of glycerol having the enol ethers double bond conjugated in sequence, to an acetylenic and an olefinic bond, isolated from the North-East-Atlantic sponges Raspailia pumila and R. ramosa) are stable under normal hydrolytic conditions for enol ethers. In contrast, when their solutions are evaporated, these lipids such as raspailyne Bl (=(-))-3-[(1Z,5Z)-(tetradeca-1,5-dien-3-ynyl)oxy]-1,2-propanediol;(--2) rapidly react with aerial O2 under normal laboratory-daylight conditions, with rupture of the C=C enol ether bond to give 1-O-formylglycerol (3) and an aldehyde (such as tridec-4-en-2ynal(4) from (-)-2). This reaction must be caused by triplet O2, since thermally generated singlet O2 has no effect on (-)-2 in solution. That the mere presence of an enol-ether moiety conjugated to an acetylenic group is responsible for such a behaviour is demonstrated with the model compounds 1-methoxypentadec-1-en-3-yn-5-ol (6a) and its 5-O-acetyl or 5-O-tetra-hydropyranyl derivatives 6b and 6c, respectively. Resistance to both hydroytic conditions and singlet O2 of these compounds is thought to arise from electron depletion at the enol-ether C(beta;) atom by the acetylenic group. Plausible reaction pathways for enol-ether bond rupture in these compounds by aerial O2 are outlined.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700521

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

59

Digitale Medien

Catalytic Intramolecular Palladium-Ene Reactions. Preliminay CommunicationPresented at the ‘4th IUPAC-Symposium on Organometallic Chemistry Directed towards Organic Synthesis’ (OMCOS IV), July 28, 1987, Vancouver, Canada. (1987)

Oppolzer, Wolfgang ; Gaudin, Jean-Marc

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1477-1481

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Pd(dba)2[dba = dibenzylideneacetone]/PPh3-or Pd(PPh3)4-catalyzed cyclizations of acetoxy-dienes 2 → 3 and 10 → 11 gave 1-vinyl-2-methylidene-subsituted cyclopentances and cyclohexanes in high yield, consistent with a palladium-ene/β-elimination mechanism (D → E → F, Scheme 2). The efficient and highly stereoselective cyclizations 7 → 7 and 8 → 9 illustrate intramolecular allylpalladium insertions into 1,2-dialkyl-, trialkyl-, trialkyl-, and cyclic alkenes followed by elimination of the exocyclic β-H giving 1,2-divinylcyclopentanes. These new olefin insertions proceed faster in AcOH (compared to THF) and occur preferentially cis relative to the Pd (13 → 14 → 15).

Zusätzliches Material: 2 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700604

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

60

Digitale Medien

Drug-induced modifications of the immune response part 9Part8: [1]4-(Arylamino)-2,5-dihydro-2-oxo-N-(trans-2-phenylcycolopropyl)furan-3-carboxamides as Novel Antiallergic Compounds (1987)

Georgiev, Vassil St. ; Mack, Robert A. ; Walter, David J. ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1526-1530

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The synthesis and antiallergic activity of a series of 4-(arylamino)-2,5-dihydro-2-oxo-N-(trans-2-phenyl-cyclopropyl)furan-3-carboxamides 10 are described. Treatment of N-substituted 2-amino-4,5-dihydro-4-oxofuran-3-carboxylic acids 9 with chlorooxobis(2-oxo-1,3-oxazolidin-3-yl)phosphorus (2) and an appropriate aromatic amine in the presence of Et3N, resulted in a novel 3(2H)-furanone-→2(5H)-furanone rearrangement that led to the facile preparation of the new amides 10. The latter exerted a potent antiallergic activity when tested in the dermal vascular permeability and active anaphylaxis assays in rats. The most active compound 10b inhibited the action of serotonin, histamine, and bradykinin by 94, 92, and 100%, respectively, when administered intraperitoneally to rats at doses of 100 mg/kg. The present series of 10 represents a novel class of antiallergic agents.

Zusätzliches Material: 2 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700609

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

61

Digitale Medien

Notiz über die Verwendung von 3-(Arylsulfonyl)-2-cycloalkenonen als 2-Cycloalkinon-Synthese-Equivalente (1987)

Kienzle, Frank ; Minder, Rudolf E.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1537-1539

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Note on the Use of 3-(Arylsulfonyl)-2-cycloalkenones as Synthesis Equivalents of 2-Cycloalkynones3-(Arylsulfonyl)-2-cyclopentenones and 3-phenylsulfonyl-2-cyclohexnone undergo Diels-Alder reactions with cyclopentadiene. Elimination of arylsulfinic acid leads to products, which would have been obtained directly from a Diels-Alder reaction of 2-cyclopentynone or 2-cyclohexynone.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700611

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

62

Digitale Medien

Inhibition of Electron-Hole Recombination in Substitutionally Doped Colloidal Semiconductor Crystallites (1987)

Moser, Jacques ; Grätzel, Michael ; Gallay, Roland

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1596-1604

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The subtitutional doping of 120-Å- sized TiO2 Particles with Fe(III)ions has a profound effect on the charge carrier recombination time in this colloidal semiconductor. In undoped particles, the mean lifetime of an electronhole pair is ca. 30 ± 15 ns. Doping with 0.5% Fe(III) drastically augments the charge-carrier lifetime which is extended to minutes or hours. The slow character of the recombination dynamics in Fe(III)-doped colloids was confirmed by laser photolysis using the characteristic optical of electrons in TiO2 to monitor the time course of the reaction. EPR studies showed the Fe(III) ions to enter the host lattice on Ti(IV) sites, charge compensation taking place through the formation of oxygen vacancies. Valence-band holes produced under band-gap excitation react with these centers it the bulk forming Fe(IV), the conduction band electrons being trapped by Ti(IV) at the particle surface. Presumably, the spatial separation of the trapped electron and hole sites inhibits their recombination.

Zusätzliches Material: 7 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700617

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

63

Digitale Medien

The Radical Anions of 1,2-diphenylcyclohexene and Structurally Related Compounds. Conformational ESR and ENDOR studies (1987)

Gerson, Fabian ; Martin, Williiam B.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1558-1568

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: ESR, ENDOR, and TRIPLE resonance studies have been performed on the radical anions of 1,2-diphenylcyclohex-1-ene (4), 1,2-di(perdeuteriophenyl)cyclohex-1-ene ((D10)4) the trans-configurated 3,4-diphenyl-8-oxabicyclo[4.3.0]non-3-ene (5) and its 2,2,5,5-tetradeuterio derivative (D4)5, and 2,3-diphenyl-8,9,10-trinorborn-2-ene (6). The spectra of \documentclass{article}\pagestyle{empty}\begin{document}$ 4^{- \atop \dot{}} $\end{document} exhibit strong temperature dependence along with a specific broadening of ESR hyperfine lines and proton ENDOR signals. The coupling constant, which bears the main responsibility for these features, is that of the β-protons in the quasi-equatorial positions of the cyclohexene ring, and the experimental findings are readily rationlized in terms of relatively modest conformational changes without invoking the inversion of the half-chair form. The hyperfine data for the β-protons in \documentclass{article}\pagestyle{empty}\begin{document}$ 5^{- \atop \dot{}} $\end{document} closely resemble the corresponding low-temperature values for \documentclass{article}\pagestyle{empty}\begin{document}$ 4^{- \atop \dot{}} $\end{document}, However, the ‘unusual’ features observed for \documentclass{article}\pagestyle{empty}\begin{document}$ 4^{- \atop \dot{}} $\end{document} are absent in the ESR and ENDOR spectra of \documentclass{article}\pagestyle{empty}\begin{document}$ 5^{- \atop \dot{}} $\end{document}, because the half-chair conformation of the cyclohexene ring in \documentclass{article}\pagestyle{empty}\begin{document}$ 5^{- \atop \dot{}} $\end{document} is deprived of its flexibility. Although the boat form of this ring in \documentclass{article}\pagestyle{empty}\begin{document}$ 6^{- \atop \dot{}} $\end{document} is also rigid, the spectra of \documentclass{article}\pagestyle{empty}\begin{document}$ 6^{- \atop \dot{}} $\end{document} are temperature-dependent, due to an interconversion between two propeller-like conformations of the phenyl groups. The pertinent barrier is 30 ± 5 kJ·mol-1. An analogous interconversion presumably takes place in \documentclass{article}\pagestyle{empty}\begin{document}$ 4^{- \atop \dot{}} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ 5^{- \atop \dot{}} $\end{document} as well, but, unlike \documentclass{article}\pagestyle{empty}\begin{document}$ 6^{- \atop \dot{}} $\end{document}, it is not amenable to experimental study.

Zusätzliches Material: 7 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700614

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

64

Digitale Medien

Synthesis and Formation of Ironcarbonyl Complexes of 3′,3′-Dimethyl-2,3,5,6-tetramethylidenespiro[bicyclo[2.2.1]heptane-7,2′-oxirane]. Single-Crystal and Molecular Structure of syn,exo2,3-anti,endo5,6-trans-μ-[(1r,2r,3s,4s,5s,6r)-c,2,3,c-η:c,5,6,c-η-(3′,3′-dimethyl-2,3,5,6,-tetramethylidenespiro[bicyclo[2.2.1]heptane-7,2′-oxirane])]bis(tricarbonyliron)Interaction between non-conjugated chromophores, Part 27. Part 26, see [1]. (1987)

Rubello, Albino ; Vogel, Pierre ; Chapuis, Gervais

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1638-1648

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The 3′,3′-dimethyl-2,3,5,6-tetramethylidenespiro[bicyclo[2.2.1]heptane-7,2′-oxirane] (3) was derived from 6,6-dimethylfulvene and maleic anhydride. Its reaction with 1 equiv. of ethylenetetracarbonitrile (TCNE) was not regioselective and gave a 1:1 mixture of the corresponding monoadducts 10 and 11. The rate constants of the Diels-Alder additions of 10 and 11 to TCNE were significantly smaller than that of the reaction 3 + TCNE. Monocomplexation of 3 with Fe2(CO)9 was highly exo-face selective giving a mixture of the corresponding monocomplexes 12(anti-exo) and 13(syn-exo). The latter were complexed with Fe2(CO)9 in a non-stereoselective fashion, giving mixtures of the dicomplexes 14(anti-exo, syn-endo), 15(anti-exo,syn-exo), and 16(anti-endo, syn-exo). Exchange of the CO ligands was a faster process for the endo-Fe(CO)3 moieties than for the exo-Fe(CO)3 moieties. Line-shape analysis of the 13C-NMR spectrum of 15 established that one of the exo-Fe(CO)3 groups in 15 rotates ca. 3 times as fast as the other Fe(CO)3 group at 40°. The structure of the anti-endo, syn-exo dicomplex 16 was determined by single-crystal X-ray diffraction studies.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700621

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

65

Digitale Medien

New Antifungal Chromenyl Ketones and their Pentacyclic Dimers from Hypericum revolutum VAHLPresented in part at the 34th Annual Congress on Medicinal Plant Research, Hamburg, FRG, 22-27 September, 1986. (1987)

Décostered, Laurent A. ; Hostettmann, Kurt ; Stoeckli-Evans, Helen ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1694-1702

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Two new 2H-1-benzopyranyl ketones 1 and 2 and three new pyrano[3,2-c: 4,5,6-d′ e′]di[1]benzopyrandiyl diketones 3, 4a/4b, and 5 have been isolated from the leaves and twigs of Hypericum revolutum VAHL (Guttiferae). The structure of 3 (hyperevoline) was established by X-ray analysis as 1,1′-[1,13,13a,13b-tetrahydro-5,8,10-trihydroxy-2,2,6,9,13,13-hexamethyl-2H, 7aH-pyrano[3,2-c:4,5,6-d′e′]di[1]benzopyran-4, 11-diyl]bis[2-methyl-1-propanone]. The structures of the isolated compounds were established by spectroscopic (UV, IR, EI-MS, 1H- and 13C-NMR) and chemical (acetylation and acidic dimerization) methods.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700705

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

66

Digitale Medien

Mammalian Alkaloids: Configurations of Optically Active Salsoline- and 3′,4′-Dideoxynorlaudanosoline-1-carboxylic AcidsSalsoline and norlaudanosoline are well known alkaloids, and these names will be used in the General Part (for systematic names, see Expert. Part). The systematic name for salsoline is 1-methyl-7-methoxy-1,2,3,4-tetrahydroisoquinolin-6-ol and that for norlaudanosoline, also named tetrahydropapaveroline, is 1-(3′,4′-dihydroxybenzyl)-1,2,3,4-tetrahydroisoquinoline-6,7-diol. (1987)

Chrzanowska, Maria ; Schönenberger, Bernhard ; Brossi, Arnold ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1721-1731

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Synthesis of the optical isomers of (±)-methyl 6,7-dimethyl-3′,4′-dideoxynorlaudanosoline-1-carboxylate ((±)-2) was accomplished by reaction of (±)-2 with (+)-(R)-1-phenylethyl isocyanate, separation of the urea diastereoisomers (-)-4A and (+)-4B, and alcoholysis of the ureas in refluxing BuOH. Optically active isoquinoline-carboxylates 2A,B and hydantoins 8A,B isolated were characterized. The absolute configuration of the reaction products was established by X-ray analysis of the optically active hydantoin (+)-8A. Hydrolysis of the methyl isoquinolinecarboxylates 2A,B with 48% HBr soln. at reflux afforded the desired optically active 3′,4′-dideoxynorlaudanosoline-1-carboxylic acids 1A,B required for enzyme-inhibition studies. Details of the X-ray diffraction analysis of (+)-methyl salsoline-1-carboxylate hydrobromide ((+)-11A·HBr) prepared earlier are included. CD spectra of (+)-(S)-methyl 6,7-dimethyl-3′,4′-dideoxynorlaudanosoline-1-carboxylate hydrobromide ((+)-2A. HBr) and (-)-(R)-methyl salsoline-1-carboxylate hydrochloride ((-)-11B·HCl) confirmed the assignment of their (S)- and (R)-configurations, respectively.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700707

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

67

Digitale Medien

Determination of the Quantum Yield of Intersystem Crossing of Rose Bengal (1987)

Murasecco-Suardi, Patricia ; Gassmann, Ernst ; Braun, André M. ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1760-1773

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The quantum yield of intersystem crossing (Φisc) of a sensitizer is related to the quantum yield of singlet-oxygen production (Φ(1O2)) by the efficiency of the energy transfer (ϕet) and is an important parameter in the evaluation of potential applications of sensitized photo-oxidations. Using two different laser photolysis techniques, the energy-transfer method and the partial saturation method, Φisc of rose bengal has been determined in MeOH and in aqueous solutions. The results confirm that with Φisc(H2O) = 1.05(± 0.06) and Φisc(MeOH)=0.90(±0.08), the generally assumed relation Φisc · ϕet = Φ(1O2), with ϕet = 1, cannot be maintained any longer (Φ(1O2, H2O) = 0.75 and Φ(1O2, MeOH) = 0.76). During these experiments, a second intermediate has been observed which is produced from the triplet state of rose bengal and, stabilized in a anionic micellar solution, has been shown to be the radical cation of the sensitizer. The efficiency of the electron transfer has been evaluated from transient absorption and bleaching recordings, and it seems conclusive to attribute the results to the difference between Φisc and Φ(1O2).

Zusätzliches Material: 8 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700712

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

68

Digitale Medien

‘Face-to-Face’-Benzo-anellierte homologe Hypostrophene. Synthesen, Röntgenstrukturanalysen und PE-Spektren (1987)

Fessner, Wolf-Dieter ; Sedelmeier, Gottfried ; Knothe, Lothar ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1816-1842

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: ‘Face-to-Face’ Benzo-anellated Homologous Hypostrophenes. Syntheses, X-Ray-Structure Analyses and PE Spectra‘Face-to-face’ Benzo-anellated homologous hypostrophenes (series M), of interest as substrates for [6 + 6]-photocycloaddition reactions, have been synthesized. From X-ray structural analyses of 13b and 13c shortest C—C distances of 2.80(2.76)/2.71 Å and interorbital angles (ω) of 129° (128°)/130° between the benzene rings have been determined. The PE spectra are discussed in the context of transannular π,π interactions.

Zusätzliches Material: 6 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700718

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

69

Digitale Medien

Formation and Structure of the Phosphoranyl Radical Derived from 1,2-Phenylene Phosphorochloridate: a Solid-State ESR Study (1987)

Cattani-Lorente, Maria ; Bernardinelli, Gérald ; Geoffroy, Michel

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1897-1904

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The crystal structure of 1,2- phenylene phosphorochloridate has been determined. X-Ray irradiation of these crystals, at low temperature, leads to the formation of a radical exhibiting hyperfine structure with P and Cl nuclei. The corresponding ESR tensors are obtained, and they show that this radical is a phosphoranyl radical adopting a slightly distorded σ* structure. The same species could be produced in frozen solution, its hyperfine tensors are, then, more in accordance with a trigonal-bipyramid structure. The effects of the host matrix on the stabilization of the structure of phosphoranyl are investigated.

Zusätzliches Material: 4 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700724

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

70

Digitale Medien

Isolierung und Strukturaufklärung von 36 Diterpenoiden aus Trichomen von Plectranthus edulis (VATKE) T.T. AYE (1987)

Künzle, Josef Max ; Rüedi, Peter ; Eugster, Conrad Hans

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1911-1929

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Isolation and Structure Elucidation of 36 Diterpenoids from Leaf-Glands of Plectranthus edulis (VATKE) T.T. AYEAnalysis of the polar diterpenoids from the yellow glands of the title plant from Kenya and Abyssinia led to the identification of several novel abietanoids. Main compound is the known edulon A (40), a 5(4→3) abeo-abietane. Minor compounds include 6 different royleanones, 15 spirocoleons, 3 vinylogous quinones, 8 acylhydroquinones (as their 6,7-dioxo compounds or the tautomeric disophenols), 2 naphthaquinones (as the 1,10-seco-abietanoids), and deacetyledulon A. The known coleon-A-lactone (37) now has also been found in Plectranthus edulis. The intermediacy of the γ-enollactol 44, combined with a leaving group on C(3) is postulted to explain the biogenesis of the unusual 4H-5-oxaaceanthrylen skeleton of edulon A.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700726

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

71

Digitale Medien

Synthesis of trans-10,11-Dihydro-10,11-dihydroxy-5H-dibenz[b,f]azepine-5-carboxamide, a Major Metabolite of Carbamazepine (1987)

Heckendorn, Roland

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1955-1962

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The stereoselectivity of the reduction of 5-carbamoyl-10,11-dihydro-11-oxo-5H-dibenz[b,f]azepine-10-yl acetate (6), prepared in two steps from 10,11-dihydro-10-oxo-5H-dibenz[b,f]azepine-5-carboxamide (4), has been studied. Among the reagents used, diisobutylaluminum hydride (DIBAH) was found to give the highest trans/cis diol ratio. This allowed the preparation of the important trans-diol metabolite 3 of carbamazepine (1).

Zusätzliches Material: 2 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700730

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

72

Digitale Medien

Are the known Δ2-cephems inactive as antibiotics because of an unfavourable steric orientation of their 4α-carboxylic group? Synthesis and biology of two Δ2-cephem-4β-carboxylic acids (1987)

Cohen, Nissim C. ; Ernest, Ivan ; Scartazzini, Riccardo ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1967-1979

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Two representatives of the yet unknown type of Δ2-cephem-4β-carboxylic acids were prepared. Contrarily to the prediction based on the activity model of Cohen, both acids proved inactive as antibiotics. Possible reasons for this discrepancy are briefly discussed.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700732

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

73

Digitale Medien

Isolierung von 10′-Apo-β-carotin-10′-ol und (3R)-10′-Apo-β-carotin-3,10′-diol (Galloxanthin) aus Rosenblüten. 5. Mitteilung über Rosenfarbstoffe1. bis 4. Mitt., s. [1-4]. (1987)

Märki-Fischer, Edith ; Eugster, Conrad Hans

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 70 (1987), S. 1988-1993

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Isolation of 10′-Apo-β-carotene-10′-ol and (3R)-10′-Apo-β-carotene-3,10′-diol (Galloxanthin) from Rose FlowersThe novel (all-E)-10′-apol-β-carotene-10′-ol (2) and (all-E,3R)-10′-apo-β-carotene-3,10′-diol (5) have been isolated from petals of one yellow species and various whitish or yellow blend varieties of rose cultivars. Each (all-E)-compound is accompanied by a (Z)-isomer, probably the (9Z)-isomer. Diol 5 proved to be identical with galloxanthin, an apo-10′-carotenol previously isolated from the retina of chicken.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19870700803

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

74

Digitale Medien

Masthead (1989)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989)

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720101

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

75

Digitale Medien

The Conformation of Cycloartenol Investigated by NMR and Molecular Mechanics (1989)

Milon, Alain ; Nakatani, Yoichi ; Kintzinger, Jean-Pierre ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 1-13

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Cycloartenol (4), a natural plant sterol, was shown to be an effective membrane reinforcer; this was attributed to its conformation. We now present a conformational analysis of 4 by molecular modeling and NMR. Molecular modeling suggests that two conformations I and II coexist, differing mainly at the level of ring C, and of nearly equal energy, I and II each having ring A and B in a chair and half-chair conformation, respectively, with ring C 1,3-diplanar in I (solid-state structure as determined by X-ray crystallography) and in chair conformation in II. A complete assignment of the 1H- and 13C-NMR spectra of 4 and the entire coupling network in rings A and B is determined by various modern NMR techniques. The conformation of rings A and B thus determined is in agreement with conformations I and II. Low-temperature NMR experiments show a fast equilibrium between two conformations, presumably I and II. It is concluded, therefore, that the cyclopropane ring of 4 produces a flexibility at the level of ring C which may be important for the membrane properties.

Zusätzliches Material: 8 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720102

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

76

Digitale Medien

Palladium(0)-Catalyzed Cyclizations of Simple 1-Aryl-1,7-octadien-3-yl Acetates. Preliminary communicationPresented (W.O.) at the ‘3e Congrès national de la Société Française de Chimie’, Nice, September 5, 1988. (1989)

Oppolzer, Wolfgang ; Swenson, Rolf E. ; Pachinger, Werner

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 14-16

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Dienyl acetates 2 lacking a geminal disulfone or a malonate group cyclize selectively to (E)-l-methylidene-2-styrylcyclopentanes 4 in the presence of 7 mol-% of [Pd(PPh3)4].

Zusätzliches Material: 1 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720103

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

77

Digitale Medien

Über den Einfluss des Akzeptor-Teilchromophors bei Dimethin-merocyanin-Farbstoffen auf das Aggregationsverhalten in wässriger Lösung (1989)

Kussler, Manfred ; Balli, Heinz

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 17-28

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: On the Influence of the Acceptor Part of the Chromophor of Dimethinemerocyanine Dyes upon the Aggregation Tendency in Aqueous SolutionA series of novel long-chain alkyl-dimethinemerocyanine dyes containing sulfonate groups is synthesized in good yield and their aggregation tendency in H2O and in organic solvent/H2O mixtures investigated. The merocyanine dyes 11 and 15 only exhibit an intense, red-shifted absorption band due to J-aggregation in H2O without addition of salt. The influence of cationic and anionic tensides and other compounds as urea, glucose, and polysaccharides upon the J-aggregation tendency is investigated.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720104

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

78

Digitale Medien

Generation and Trapping of TriafulveneFulvene, Fulvalenes, Part 55; Part 54: [1].Short communication: [2]. (1989)

Weber, Andreas ; Stämpfli, Urs ; Neuenschwander, Markus

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 29-40

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Substituted methylidenecyclopropanes 12a-d, being easily available from 1,1-dibromo-2-(phenylthio)-cyclopropane (9a), are attractive precursors of triafulvene (2-methylidene-1-cyclopropene; 1). Both the sulfoxide 12b and the sulfone 12c react with an excess of alkoxides (t-BuOK and NaOMe) to give 12e and 12f, respectively, while the sulfinyl group of 12b may be replaced by the PhCH2S substituent in the presence of PhCH2SH/t-BuOK. These reactions (Scheme 4) may be explained by assuming 1 as a reactive intermediate, although an alternative sequence including carbene 20 (Scheme 6) is not completely ruled out. D-labelling experiments (Scheme 5) do not give conclusive evidence due to D scrambling, but deprotonation/methylation sequences show that H—C(2) of 12a-c is the most acidic proton. Final evidence for 1 results from the reaction of 12d with cyclopentadienide (Scheme 7): the reaction of 1 with cyclopentadiene produces the expected [4 + 2]-cycloaddition product 23, while some mechanistic insight results from the sequence 12d → 24 → 25.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720105

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

79

Digitale Medien

A Nonconcerted Intramolecular Diels-Alder Reaction of Chiral Allenic-Acid Derivatives (1989)

Trifonov, Latchezar S. ; Orahovats, Alexander S.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 59-64

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The reaction between the chiral allenic acid (+)-(S)-1 and the carbodiimides 2a-d and the keten-imine 6 gives, under mild conditions, the tricyclic compounds 3-5, 7, and 8. Low diastereoselectivity and a partial loss of optical activity are observed. A stepwise mechanistic pathway via a biradical intermediate is postulated.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720108

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

80

Digitale Medien

Konkurrenz von Endoperoxid- und Hydroperoxid-Bildung bei der Umsetzung von Singulett-Sauerstoff mit cyclischen, konjugierten Dienen. Teil I (1989)

Matusch, Rudolf ; Schmidt, Gerhard

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 51-58

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Competition of Endoperoxide and Hydroperoxide Formation in the Reaction of Singlet Oxygen with Cyclic, Conjugated DienesRose-bengal-sensitized photooxygenation of (-)-(R)-α-phellandrene (1) in MeOH at room temperature yielded a complex mixture of products, contrary to previous reports describing cis-(3S, 6R)-epidioxy-p-menthene (2) and trans-(3R, 6S)-epidioxy-p-menthene (3) as the only products. The mixture was separated by prep. HPLC (silica gel, pentane/Et2O 9:1). Besides the known endoperoxides 2 (yield 39%) and 3 (26%), all those hydroper-oxides, which can be deduced from an ene reaction of 1O2 with 1, were isolated, i.e. 4β-p-mentha-2,5-dien-1β-yl hydroperoxide (4) (14%), 4β-p-mentha-2,5-dien-1α-yl hydroperoxide (5) (9%), (2R, 4R)-p-mentha-1(7), 5-dien-2-yl hydroperoxide (6) (2,1%), (2S, 4R)-p-mentha-1(7),5-dien-2-yl hydroperoxide (7) (1,5%) and (1R)-p-mentha-3,6-dien-yl hydroperoxide (8; 1,5%; Scheme 1). Furthermore, the constant cis/trans ratio for all diastereoisomeric pairs (2/2, 4/2, 6/2) was striking. With the help of the two possible conformers 1a and 1b of the starting material a model of a common first step for endoperoxide as well as for hydroperoxide formation is developed. A photooxygenation at -50° supports this model. The absolute value of the cis/trans ratio changes in the same way for the endoperoxides and the hydroperoxides.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720107

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

81

Digitale Medien

Versuche zur Synthese von Calicen aus trisubstituierten Cyclopropanen und Cyclopentenon56. Mitt. über Fulvene, Fulvalene; 55. Mitt. [1]: Kurzmitt. (1989)

Weber, Andreas ; Galli, Roberto ; Sabbioni, Gabriele ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 41-50

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Attempted Synthesis of Calicene from Trisubstitued Cyclopropanes and CyclopentenoneThe Li carbenoids 4, prepared by treatment of substituted 1,1-dihalocyclopropanes with BuLi, are reacted with cyclopent-2-enone under thermodynamic and kinetic control (Scheme 1). In general, the latter procedure gives better yields of cyclopropylcyclopentenols 5a-e, but the reaction seems to be controlled mainly by the steric and electronic properties of the substituent Y. So, with 4b and 4e, the main reaction is the attack of the carbenoid at C(1) of cyclopent-2-enone, while 4a (Y = PhS) predominantly deprotonates the ketone (Scheme 4). Whereas 5d and 5e can easily be converted to the dihydrocalicenes 6d and 6e (Scheme 6), the attempted elimination of H2O from 5a-c leads to the rearranged products 13-2 due to the opening of the cyclopropane ring (Scheme 5). Finally, the generation of the parent compound 2 from the silylated precursor 6d is attempted: treatment with MeO- gives the addition products 18A/18B, while the reaction with Br2 provides 19 by a bromination/dehydrobromination sequence (Scheme 7).

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720106

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

82

Digitale Medien

Locoselective [4 + 2] Cycloadditions of Vinylindoles with Inverse Electron Demand: A new access of indolyl-substituted and annellated pyridazinesDedicated to Prof. Dr. C. H. Brieskorn (Würzburg, FRG) on the occasion of his 75th birthday (1989)

Pindur, Ulf ; Pfeuffer, Ludwig ; Kim, Myung-Hwa

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 65-72

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: 2-Vinylindole (1a) and its donor- and acceptor-substituted (E)-derivatives 1b-e react highly locoselectively with dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate (3) to form the novel (indol-2-yl)-1,4-dihydropyridazines 4a and 7 as well as the heterocyclic annellated pyridazines 4b, 5, and 6. The reactions of the structurally related 3-vinylindoles 2a-e with 3 also gave rise to new indol-3-ylpyridazines 8, 9, and 10. The locoselectivities of these Diels-Alder reactions were controlled mainly by steric effects.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720109

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

83

Digitale Medien

Photochemistry of Thiophen-2(5H)-onesDedicated to Prof. Dr. O. E. Polansky on the occasion of his 70th birthday (1989)

Kiesewetter, René ; Margaretha, Paul

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 83-92

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Mechanistic evidence for the light-induced ring opening of thiophen-2(5H)-ones 1 in alcohols affording α, β-unsaturated mercapto esters 2 is presented. Regio-and stereochemical aspects of the ring closure of alkenylthio (type 3) radicals 15 and 17 to S-heterocycles 16 and 18, of 3-thiahex-5-enyl radicals 4 to (tetrahydrothien-3-yl)methyl radicals 6 and of (2,3-dihydrothien-3-yl)methyl radicals 30 (type 7, but-3-enyl radicals) to cyclopropane-methyl radicals 29 are discussed. Irradiation (λ 350 nm) of 1 in cyclohexane in the presence of 2,3-dimethylbut-2-ene affords [2 + 2] cycloadducts 14 albeit in very low yields.

Zusätzliches Material: 1 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720111

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

84

Digitale Medien

Electronic and Molecular Structure of the C8H10+· Valence Isomers 1,3,5-Cyclooctatriene+· and Bicyclo[4.2.0]octa-2,4-diene+· from their Electronic absorption Spectra in Freon (1989)

Bally, Thomas ; Roth, Kuno ; Straub, Rolf

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 73-82

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The molecular cations of 1,3,5-cyclooctatriene (COT+·) and bicyclo[4.2.0]octa-2,4-diene (BCO+·) can be observed intact in γ-irradiated Freon glasses, as opposed to Ar matrices where ionization is accompanied by extensive rearrangements. This proves the superiority of the Freon-glass method for the generation of metastable primary cations. The electronic absorption (EA) spectra reveal a) that a previous analysis of the BCO+· electronic structure on the basis of the ultraviolet photoelectron (UP( spectrum of BCO was incomplete, and b) that COT undergoes planarization upon ionization, in accord with qualitative expectations and MNDO calculations. A previously proposed LCBO model was used to assess the influence of the above geometry change on the electronic structure of COT+·.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720110

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

85

Digitale Medien

Cyclization Studies with N-Mannich bases of 2-substituted indoles (1989)

Burger, Ulrich ; Bringhen, Alain O.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 93-100

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The synthesis of the indoles 7, 15, 16 with a 3-methoxyphenyl group, attached via an α-side chain of 1,2,or 3 CH2 units, is reported. These compounds, after appropriate protection at C(3), were transformed into the N-[(dimethylamino)methyl]indoles 22, 23, and 24, respectively. When treated with AcCl, these N-Mannich bases gave, in two cases, stable N-(chloromethyl)indoles 25 and 26. In the presence of SnCl4, ring closure occurred via electrophilic attack of 1-methylideneindolium ions on the methoxyphenyl group. Formation of seven-membered rings (→ 27, 28) and eight-membered rings (→ 29) was found to be a favorable process. Cyclization to six-membered rings did not occur within this series.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720112

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

86

Digitale Medien

Template-Dependent Incorporation of Spin-Labeled Thymidine Analogs into Viral DNA (1989)

Pauly, Gary T. ; Bobst, Elisabeth V. ; Bruckman, David ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 110-116

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The synthesis of novel pppUd analogs substituted at position C(5) with tethered nitroxide radicals is reported. It is shown that these analogs can serve as good substrates for E. coli DNA polymerase (Pol I) and T-4 DNA polymerase using lambda-phage DNA as template. The template-dependent incorporation of the substrates was established by radio-labeling and ESR experiments.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720114

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

87

Digitale Medien

Stereoselektive Synthesen von Taxan-Derivaten (1989)

Neh, Harribert ; Kühling, Andrea ; Blechert, Siegfried

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 101-109

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Stereoselective Synthesis of Taxane DerivativesSubstituted racemic 4,8,12-trinortaxanes were prepared stereoselectively in several steps from the dienone 10. A variant of the de Mayo reaction with bicyclononenones 4 and cyclohexen produced the desired configuration at C(8) of the taxane framework. Retro-aldol cleavage of the tetracycle 5 led to the taxane skeleton 6. Stereoselective reduction followed by treatment with base afforded 7b. Hydrolysis of the acetal group and further reduction yielded 9 in which the relative configuration corresponds to the one of the natural products.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720113

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

88

Digitale Medien

Asymmetric Diels-Alder reactions: X-Ray crystal-structure analysis of [N-((E)-But-2-enoyl)bornane-10,2-sultam]tetrachlorotitaniumPresented (WO) at the Annual Congress of the Royal Society of Chemistry, Canterbury, April, 1988. (1989)

Oppolzer, Wolfgang ; Rodriguez, Inès ; Blagg, Julian ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 123-130

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: An X-ray diffraction analysis of the crystalline complex 2b (MLn — TiCl4) shows a chelation of the carbonyl O-atom and the upper SO2 O-atom by TiCl4, a slightly pyramidal N-atom, and a π -face-stereoselective shielding of the C(α)-Si face by the CH2(3) group. The Ti-atom is in a pseudo-octahedral environment.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720116

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

89

Digitale Medien

Metal Complexes with Macrocyclic Ligands. Part XXVIIPart XXVI. Cu2+-promoted hydrolysis of carboxylic- and phosphonic-acid esters in the side chain of tetraazamacrocycles (1989)

Tschudin, Daniel ; Riesen, Andreas ; Kaden, Thomas A.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 131-138

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The X-ray structures of the Cu2+ complexes of 1,4,8,11-tetraazacyclotetradecane derivatives with an ethylpro-pionate and diethylphosphonate group, 5 and 6, respectively, indicate that the metal ion is pentacoordinated by the four N-atoms of the macrocycle and one O-atom. In the case of 5, it is the carbonyl O-atom of the carboxylate group, whereas for 6 it is the phosphonyl O-atom of the phosphonate group. The hydrolysis kinetics of the functional group in the Cu2+ complexes with the 1,4,8,11-tetraazacyclotetradecanes 3-6 have been measured by pH-stat and stopped-flow techniques. The rate law for the hydrolysis of the carboxylates 3-5 is proportional to the complex concentration and to [OH-] up to pH 13, whereas that of the phosphonate 6 is proportional to [OH-] up to pH 11.5, becoming independent of [OH-] at pH 〉 11.5. The mechanisms of these two reactions are discussed, considering the possibility of an intra- or an intermolecular OH- attack and the results of the X-ray structure analyses.

Zusätzliches Material: 5 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720117

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

90

Digitale Medien

A New Method for the Preparation of (E)-3-Acylprop-2-enoic AcidsPresented in part at the autumn meeting of the Swiss Chemical Society in Bern on October 21, 1988.Dedicated to Prof. R. E. Ireland on the occasion of his 60th birthday (1989)

Obrecht, Daniel ; Weiss, Bettina

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 117-122

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: A new method for the preparation of (E)-3-acylprop-2-enoic acids ( = (E)-3-acylacrylic acids) of type II via acid-catalyzed isomerization of the corresponding 3-acylprop-2-ynal acetals of type I (Scheme 1) has been found. The described reaction gives a rapid and quite general access to these compounds known to exhibit a number of interesting biological activities. Some studies toward the elucidation of the reaction mechanism have been made, and a hypothetical mechanism is proposed.

Zusätzliches Material: 2 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720115

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

91

Digitale Medien

6-Thia-1-aza-5λ5-phosphabicyclo[3.2.0]hept-3-ene und Isothiocyanatophosphin-sulfide aus (Methylidenamino)phosphinen, Schwefelkohlenstoff und Acetylen- oder Ethylen-Derivaten (1989)

Fulde, Maria ; Ried, Walter ; Bats, Jan W.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 139-146

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: 6-Thia-l-aza-5λ5-phosphabicyclo[3.2.0]hept-3-enes and Isothiocyanatophosphine-sulfides from (Methylidenamino)phosphines, Carbon Disulfide, and Acetylene- or Ethylene Derivatives(Methylidenamino)phosphines react with carbon disulfide to 1,3,2-thiazaphosphete derivatives 2. Acetylenedicarboxylates give with 2 6-thia-l-aza-5λ5-phosphabicyclo[3.2.0]hept-3-enes 4a, b, and acrylates yield isothio-cyanatophosphin-sulfides 5a-c. The structures of 4a and 5a are proven by an X-ray diffraction analysis.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720118

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

92

Digitale Medien

C45 und C50-Carotinoide. 6. Mitteilung5. Mitteilung, s. [1]. Synthese eines optisch aktiven cyclischen C20-Bausteins und von Decaprenoxanthin (= (2R, 6R, 2′R, 6′R)-2,2′-Bis(4-hydroxy-3-methylbut-2-enyl)-∊, ∊-carotin) (1989)

Gerspacher, Marc ; Pfander, Hanspeter

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 151-157

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: C45- and C50-Carotenoids: Synthesis of an Optically Active Cyclic C20-Building Block and of Decaprenoxanthin ( = (2R, 6R, 2′R, 6′R)-2,2′-Bis(4-hydroxy-3-methylbut-2-enyl)-∊, ∊-carotene)The synthesis of the optically active cyclic C20-building block (R, R)-15 and of the optically active C50-carotenoid (2R, 6R, 2′R, 6′R)-decaprenoxanthin (1) starting from (-)-β-pinene ((S)-2) is reported.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720120

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

93

Digitale Medien

Formation of the First Trimeric Monoterpenoid Indole Alkaloids (1989)

Schübel, Helmut ; Fahn, Walter ; Stöckigt, Joachim

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 147-150

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Under O2, the Aspidosperma alkaloid tabersonine (1) was converted by a crude enzyme preparation from leaves of mature plants of Catharanthus roseus G DON into the trimeric 3-hydroxy-14′-(3α″-tabersonyl)voafrine B (4) which was easily reduced by NaBH4 to 14′-(3α″-tabersonyl)voafrine B ( = tertabersonine; 5). Compounds such as 4 and 5 are the first trimeric alkaloids in the series of monoterpenoid indole alkaloids.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720119

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

94

Digitale Medien

Polynuclear Iron and Rhodium Complexes of 7-Oxa[2.2.1]hericene (2,3,5,6-tetramethylidenebicyclo[2.2.1]heptan-7-one) (1989)

Rubello, Albino ; Vogel, Pierre

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 158-164

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: μ-Carbonyl(Rh—Rh)di(η5-indenyl)[(2R,3S)-C,2,3,C-η-(2,3,4,5-tetramethylidenebicyclo[2.2.1]heptan-7-one)]]-dirhodium(I)(Rh—Rh) (7) and cis-μ-[(2R,3S,5R,6S))-C,2,3,C-η:C,5,6,C-η-(2,3,5,6-tetramethylidenebicyclo[2.2.1]heptan-7-one)]bis[μ-carbonyldi(η5-indenyl)dirhodium(I)(Rh—Rh)] (8) have been prepared. Complex 7 reacts with Fe2(CO)9 in hexane/MeOH and gives cis-μ-[(2R,3S,5R,6S] (9), trans-μ-[(2R,3S,5S,6R)-C,2,3,C-η: C,5,6, C-η-(2,3,5,6-tetramethylidenebicyclo[2.2.1]heptan-7-one)-μ-carbonyldi(η5-indenyl)dirhodium(I)(Rh—Rh)-(tricarbonyliron) (10), and, μ-carbonyl(Rh—Rh)[(2R,3S)-C,2,3,C-η-(2,3-dimethyl-5,6-dimethylidenebicyclo-[2.2.1]hept-2-en-7-one)]di(η5-indenyl)dirhodium(I)(Rh—Rh) (11). Treatment of 7-oxa[2.2.1]hericene (4) with Fe2(CO)9 or (cyclooctene)2Fe(CO)3 gave a 1:2 mixture of cis-μ-[(2R,3S,5R,6S)-] (12) and trans-μ-[(2R,3S,5S,6R)-C,2,3,C-η:C,5,6,C-η-(2,3,5,6-tetramethylidenebicyclo[2.2.1]heptan-7-one)]bis(tricarbonyliron)(13).

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720121

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

95

Digitale Medien

Eine neue Aminoazirin-Reaktion. Bildung von 3,6-Dihydropyrazin-2(1H)-onen (1989)

Hugener, Martin ; Heimgartner, Heinz

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 172-179

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: A New Aminoazirine Reaction. Formation of 3,6-Dihydropyrazin-2(1H)-onesThe reaction of 3-(dimethylamino)-2H-azirines 1 and 2-(trifluoromethyl)-1,3-oxazol-5(2H)-ones 5 in MeCN or THF at 50-80° leads to 5-(dimethylamino)-3,6-dihydropyrazin-2(1H)-ones 6 (Scheme 3). Reaction mechanisms for the formation of 6 are discussed: either the oxazolones 5 react as CH-acidic heterocycles with 1 (Scheme 4), or the azirines 1 undergo a nucleophilic attack onto the carbonyl group of 5 (Scheme 6). The reaction via intermediate formation of N-(trifluoroacetyl)dipeptide amide 8 (Scheme 5) is excluded.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720123

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

96

Digitale Medien

Synthesis of the Oviposition-Deterring Pheromone (ODP) in Rhagoletis cerasi L. Preliminary communication (1989)

Ernst, Beat ; Wagner, Beatrice

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 165-171

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: For the assignment of the configuration at C(8) and C(15) of the natural oviposition-deterring pheromone 1 in Rhagoletis cerasi L., the four possible stereoisomers of 1 are synthesized. By condensing the C6 building blocks (5R)-4 and (5S)-4 with the boron enolates of the C10 building blocks (4S)-13 and (4R)-13, followed by decarboxylative dehydration, all stereoisomers of 16 are available (Scheme 5). Glucosylation of 16 followed by formation of the taurin amide gives, after deprotection, the four stereoisomers (8R,15S)-1, (8R,15R)-1, (8R,15S)-1, and (8S,15S)-1 (Scheme 6).

Zusätzliches Material: 1 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720122

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

97

Digitale Medien

Mitteilungen (1989)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 185-192

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720125

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

98

Digitale Medien

New Spermine Alkaloids from Aphelandra tetragona (VAHL) NEESDedicated to Prof. Dr. D. Gröger on the occasion of his 60th birthday (1989)

Tawil, Bassem F. ; Zhu, Ji-Ping ; Piantini, Umberto ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 180-184

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: 18-O-Methylchaenorpine (1a) and iso-18-O-methylchaenorpine (1b) two novel stereoisomeric spermine alkaloids were isolated from the roots of Aphelandra tetragona (VAHL) NEES. Their structures were established by chemical and spectroscopic studies.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720124

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

99

Digitale Medien

Masthead (1989)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989)

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720201

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

100

Digitale Medien

1,5,7-Triazabicyclo[4.4.0]dec-5-en als Reaktionsmedium: Präparativ ergiebige einstufige Herstellung von Etioporphyrin aus Protoporphyrin (1989)

Kämpfen, Ulrich ; Eschenmoser, Albert

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 72 (1989), S. 185-195

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: 1,5,7-Triazabicyclo[4.4.0]dec-5-ene as Reaction Medium: An Efficient One-Step Formation of Etioporphyrine from ProtoporphyrineHeating the commercially available protoporphyrine (4) in molten 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) at 200° for 4 h under exclusion of O2 produces etioporphyrine (6) in 60-70% yield by bisdecarboxylation and concomitant reduction of the two vinyl groups. Mesoporphyrine (5) is bisdecarboxylated to 6 in over 80% yield under these conditions in TBD as well as in DBU as the reaction medium.

Zusätzliches Material: 7 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19890720202

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext