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1

Digitale Medien

Animals as indicators of ecosystem responses to air emissions (1984)

Newman, James R. ; Schreiber, R. Kent

Springer

Environmental management 8 (1984), S. 309-324

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ISSN: 1432-1009

Schlagwort(e): Animals ; Indicators ; Air pollution ; Ecosystem responses

Quelle: Springer Online Journal Archives 1860-2000

Thema: Energietechnik

Notizen: Abstract With existing and proposed air-quality regulations, ecological disasters resulting from air emissions such as those observed at Copperhill, Tennessee, and Sudbury, Ontario, are unlikely. Current air-quality standards, however, may not protect ecosystems from subacute and chronic exposure to air emissions. The encouragement of the use of coal for energy production and the development of the fossil-fuel industries, including oil shales, tar sands, and coal liquification, point to an increase and spread of fossil-fuel emissions and the potential to influence a number of natural ecosystems. This paper reviews the reported responses of ecosystems to air-borne pollutants and discusses the use of animals as indicators of ecosystem responses to these pollutants. Animal species and populations can act as important indicators of biotic and abiotic responses of aquatic and terrestrial ecosystems. These responses can indicate long-term trends in ecosystem health and productivity, chemical cycling, genetics, and regulation. For short-term trends, fish and wildlife also serve as monitors of changes in community structure, signaling food-web contamination, as well as providing a measure of ecosystem vitality. Information is presented to show not only the importance of animals as indicators of ecosystem responses to air-quality degradation, but also their value as air-pollution indices, that is, as air-quality-related values (AQRV), required in current air-pollution regulation.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01868030

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2

Digitale Medien

The He(Iα) Photoelectron Spectra of the Perfluoroderivatives of Trisannelated Benzenes and Tetrakisannelated Cyclooctatetraenes (1984)

Heilbronner, Edgar ; Wirz, Jakob ; Soulen, Robert L.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 47-53

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The He(Iα) photoelectron (PE) spectra of tris(perfluorocyclobuta)benzene 4(F)3,3,4,4,7,7,8,8,11,11,12,12-Dodecafluorotetracyclo[8.2.0.02,5.06,9]dodeca-1,5,9-triene, tris(perfluorocyclopenta)benzene 5(F)1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-Octadecafluoro-2,3,4,5,6,7,8,9-octahydro-1H-trindene., tetrakis(perfluorocyclobuta)cyclooctatetraene 6(F)3,3,4,4,7,7,8,8,11,1l,l2,l2,l5,15,16,16-Hexadecafluoropentacyclo[12.2.0.02,5.06,9.010,13]hexadeca-1,5,9,13-tetraene., and of tetrakis(perfluorocyclopenta)cyclooctatetraene 7(F)1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12-Tetracosafluoro-1,2,3,4,5,6,7,8,9,10,11,12-dodeca-hydrotetracyclopenta[a,c,e,g]cyclooctene. are reported. A tentative assignment of the PE spectra is derived by empirical correlation with those of relevant reference compounds. The results suggest that 6(F) retains the D4h-conformation in the gas phase, i.e. A conformation with a planar cyclooctatetraene ring, as observed in the crystal. All four compounds exhibit a sharp increase of their first ionization energies, relative to the corresponding parent hydrocarbons, due to the perfluoro effect.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670107

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3

Digitale Medien

Transition metal complexes with bidentate ligands spanning trans-positions. Part XIVPart XIII: see [1].. Some complexes of 2,11-bis(diphenylphosphinomethyl)benzo[c]phenanthrene with platinum (0) and their reactivities (1984)

Boron-Rettore, Patrizia ; Grove, David M. ; Venazi, Luigi M.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 65-72

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The ligand 2,11-bis(diphenylphosphinomethyl)benzo[c]phenanthrene (1) has been used to prepare complexes of the type [PtL(1)] (L = C2H4, CH2=CH—CO2Me, PhC≡CPh, MeC≡CMe, MeO2CC≡CCO2Me, (i-Pr)O2CC≡CCO2(i-Pr), Ph3P and CO). It is shown that these complexes are less labile than the corresponding species [PtL(Ph3P)2]. The preparation of complexes trans-[PtX(R)(1)] by oxidative addition of RX (RX = PhCH2Br and Mel) to [Pt(C2H4)(1)] is described. The isolation of [PtO2(CH3)2CO(1)] is also reported.

Zusätzliches Material: 3 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670109

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4

Digitale Medien

Intermolecular Electron Spin Transfer between Naphthalene π-Systems Separated by a Variable Number of Spirobonded Cyclobutane Rings, An. ESR and ENDOR Study (1984)

Gerson, Fabian ; Huber, Walter ; Martin, Wiliam B. ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 416-424

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The radical anions of the compounds N1N, N3N and N5N, in which two naphthalen π-systems are separated by 1, 3 and 5 spirobonded cyclobutane rings, respectively, and tha tof the reference compound N1, containing one naphthalene π-system and one cyclobutane ring, have been studied by ESR and ENDOR spectroscopy under a variety of experimental conditions. The intramolecular electrons spin transfer between the two π-moieties in N3N.⊖ and N5N.⊖ is slow on the hyperfine time-scale, irrespective of the applied conditions. It is also slow in N1N.⊖, except for media of high solvating power. In such media, with a slight reduction of N1N to its radical anion, a paramagnetic species is observed, the hyperfine data for which are consistent with N1N to its radical anion, a paramagnetic species is observed, the hyperfine data of which are consistent with N1N.⊖, undergoing a fast intramolecular electron spin tansfer. The ESR and ENDOR spectra of this species are superimposed on those characteristic of a slow transfer. It is suggested that the fast and slow transfer involve the syn- and anti-conformations, respectively, since the distance, r, between the two naphthalene π-systems of N1N.⊖ is considerably shorter in the former than in the latter (r = 740 vs. 880 Pm for the distance between the centres of the π-systems). Glassy solutions of exhaustively reduced N1N display signals of the dianion triplet state, whereas no such signals are found for N3N and N5N. The zero-field splitting parameter, D, is 4.7 mT, corresponding to r ≈ 480 pm.

Zusätzliches Material: 5 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670210

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5

Digitale Medien

The mass spectra of organic compounds. 7th Communication6th Communication, see [1].. 4,4-Dimethyl-1-pentene (1984)

Marques, José Carlos Antunes ; Falick, Arnold ; Heusler, Andréas ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 425-433

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Loss of CH3., CH4, C2H4, C3H5., C3H6 and C3H7 from the molecular ions of a number of 13C-labeled analogs of 4,4-dimethyl-1-pentene was studied both in normal (source) 70-eV electron impact (EI) spectra dn in metastable spectra. For loss of CH3. in the source, 96% of the methyl comes frm positions of 5, 5′ and 5″, while the remainder comes from position 1. In the metastable spectra, loss of C-1 (16%) and C-3 (9%) is increasing in importance. The loss of ethylene is a particular case: either C-1 or C-3 are lost with any other C-atom from positions 2,5,5′, and 5″ (8 × 10%) in the metastable spectra, the probability for simultaneous loss of C-1 and C-3 being 6%. If C-1 seems to these two positions become completely equivalent in the metastable time range. The T-values (kinetic energy release) for the different positions show small, but statisticaly different values and a small isotope effect. Loss of C3H5 (allylic cleavage) is 100% C-1, C-2 and C-3, i.e., no evidence for skeletal rearrangement is seen. This is also true for loss of C3C6 (McLafferty rearrangement) within the source, but in metastable decay the other positions gain in importance. The neutral fragment C3H7. appears to be the the result of consecutive loss of CH3. and C3H4, rather than a one-step loss of propyl radical or the inverse reactions sequence. No metastable reaction can be seen for this reaction. Decomposition of labeled C6H11+ and C5H10+ secondary ions occurs in an essentially random fashion.

Zusätzliches Material: 6 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670211

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6

Digitale Medien

Synthese von para-substituierten phenyl-terpyridin liganden (1984)

Spahni, Werner ; Calzagerri, Gion

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 450-454

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Up to now the synthesis of para-substituted phenyl-terpyridine ligands was difficult with respect to the purification of the reaction products. We have found that these compounds can easily be isolated as hydrobromides from acetic acid. Starting from the hydrobromides the purification turned out to be easy. Synthesis of para-substituted Cl-, Br-, H3C-, H2BrC-, HO- 2,6-Bis(2-pyridyl)-4-phenylphyridine is reported.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670214

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7

Digitale Medien

Complexation de l'argent(I) par des teramines cycliques (1984)

Suet, Elisabeth ; Laouenan, André ; Handel, Henri ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 441-449

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Complexation of Silver(I) by Cyclic TetraminesThe nature of Ag(I)-complexes with 1,4,8,11-tetraazacyclotetradecane (1), 1,5,9,13-tetraazacyclohexadecane (2) 1,5,10,14-tetraazacyclooctadencane (3) and 1,6,11,16-tetraazacycloeicosane (4) is studied. The effect of ring size on disproportionation of the Ag() cation in the presence of ligand is reported. The stability of Ag(I)-complexes with 3 and 4 in aqueous solution is determined by means of potentiometric titration.

Zusätzliches Material: 5 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670213

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8

Digitale Medien

Mitteilungen - Communications (1984)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 625-627

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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.19840670231

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9

Digitale Medien

Masthead (1984)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984)

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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.19840670301

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10

Digitale Medien

Radikalionen von überbrückten [14] Annulenen. Untersuchungen zum Frontorbitaleinfluss auf Reaktivität und Bindungszustand (1984)

Huber, Walter

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 625-639

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Radical Ions of Bridged [14] Annulenes. Investigations on the Influence of Frontier Orbitals on Reactivity and BondingThe radical anions and the radical cations derived from trans-15, 16-dimethyl-1, 4:8,11-ethandiyliden[14]annulene (6), trans-15-methyl-1,4:8,11-ethandiyliden[14]annulene (7) and cis-15, 16-propano-1,4:8,11-ethandiyliden[14]annulene (8) are described. The hyperfine data of the radical anions 6, 7 and 8 resemble those of the structurally related radical anions of trans-10b, 10c-dimethyldihydropyrene (4) and trans-10b, 10c-dihydropyrene (5). This finding leads to the conclusion, that the change in the relative arragement of the saturated bridge within the fourteen-membered π-perimeter by passing from 4 (5) to 6 (7, 8) does not in fluence the energetic sequence of the lowest unoccupied molecular orbitals. The behavior of 6 and 7 towards oxidation parallels the photochemical reactivity of 4. The hyperfine coupling constants of the radical cations derived from 6 and 7 indicate that the removal of an electron is accompanied by an isomerization of the molecular framework. The investigation of the electron transfer process gby cyclic voltammetry supports these findings. The radical cations prefer the cyclophane-like structures 6a and 7a, in which the central σ-bond (C(15)-C(16) bond) is broken.

Zusätzliches Material: 7 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670302

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11

Digitale Medien

Photochemistry of 2-(Trifluoromethyl) cyclohexanone (1984)

Semisch, Christoph ; Margaretha, Paul

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 664-668

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The photochemical behaviour of the title compound 1a is compared to that of the non-fluorinated parent ketone 2-methylcyclohexanone (1b). Substitution of the CH3- group on C(2) by a trifluoromethyl group strongly enhances 2H- and RH- reduction product formation in cyclohexane or 2-propanol and oxetane formation in the presence of 2-methylpropene as olefinic component. Under all these conditions 1b exclusively undergoes a-cleavage, a process observed for 1a only in non-reducing solvents as benzene or tert-butyl alcohol.

Zusätzliches Material: 2 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670305

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12

Digitale Medien

Synthesis of Optically Pure Compounds by Enantiotopically Differentiating Monoacetalization of Prochiral Diketones. Part II. Fragmentation of β-Keto-AcetalsPart I: [1]. These results, which have been presented in part at the ‘Herbstversammlung der Schweizerischen Chemischen Gesellschaft’, October 16, 1981, in Bern, are comprised in the Ph. D. thesis of P. M. [2]. The nomenclature and classification of stereodifferentiating reactions proposed by Izumi & Tai [3] are used in this communication (1984)

Duthaler, Rudolf O. ; Maienfisch, Peter

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 832-844

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Treatment of β-keto-acetals, derived from non-enolisable β-diketones, with sulfonic acids in boiling benzene resuots in a smooth retro-Claisen-type fragmentation. The acetal-C-atom is thereby transformed into a carboxylic ester via a dialkoxycarbenium ion, which is dealkylated by the sulfonate counter-ion. Application of this reaction to the diastereomeric monoacetals 3 and 4, derived from cis-9-methyl-decalin-1,8-dione (1), followed by transesterification with CH3OH, yields optically pure 4-(2′-methyl-3′-oxocyclohexyl)butyrate 9 ((+)-9 from 3, (-)-9 from 4) and the monosulfonate of Meso-2,3-butanediol (-)-13 (Scheme 2). Unexpectedly, this cleavage proceeds as well with monoacetal 26, obtained by acetalization of trans-9-methyl-decalin-1,8-dione (27) with 2,2-dimethyl-1,3-propanediol (Scheme 7). Some attempts, aiming at an isomerization of the cis- and trans-decalin derivatives 3 and 24, or 25 and 26, via the postulated carboxonium intermediate, were not successful.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670324

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13

Digitale Medien

Preparation of Bicyclo[3.3.0]octane-2,8-dione- and Declain-1,8-dione-DerivativesThese results are comprised in the Ph. D. thesis of P. M. [1] (1984)

Duthaler, Rudolf O. ; Maienfisch, Peter

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 856-865

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Alkylation of bicyclo[3.3.0]octane-2,8-dione (1), which is prepared by a modification of the procedure described in the literature, gives the methyl- and propynyl-derivatives 6 and 7 (Scheme 1). In addition to the method described previously (Scheme 2), 9-methyl-cis-decalin-1,8-dione 9 is obtainable stereoselectively either by cyclization of keto-acid 16, or by aldol cyclization of keto-aldehyde 26 and oxydation of the resulting alcohols 24 and 25 (Scheme 4). The β-keto-alcohols 24 and 25 undergo a base-catalyzed isomerization; the trans-decalin isomers 27 and 28 are not detected in this equilibrium mixture (Schemes 4 and 5)l. Monoreduction of cis-dione 9 gives the endo-alcohol 25, while 27 is the favored product of the reductin of trans-dione 10 (Scheme 4). Optically pure (+)-25 can be prepared from (9S,10R)-monoacetal 29 (Scheme 5).

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670326

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14

Digitale Medien

Synthesis of a S-(Carboxymethyl)cysteine Analog of (L-2-Amino-6-adipyl)-L-cysteinyl-D-valine and its Cell Free Biosynthetic Conversion into 6-[2-(D-2-Amino-2-carboxyethyl)thio) acetamido]penicillanic Acid (1984)

Shields, James E. ; Campbell, Charles S. ; Duckworth, Dale C. ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 870-875

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: A new tripeptide (dimer), bis[(L-cysteine-S-acetyl)-L-hemicystinyl(S2 → S2)-D-valine] (6) was synthesized by coupling N-(tert-butoxycarbonyl)-S-carboxymethyl-L-cysteine benzyl ester (1) with S-trityl-L-cysteinyl-D-valine benzyl ester and subsequent removal of the protecting groups. After reduction of the disulfide, the free tripeptide Cys (CH2CO-Cys-D-Val) (Ib) was used as a substrate of isopenicillin-N synthetase in a cell-free conversion to 6-[2-((D-2-amino-2-carboxyethyl)thio)acetamido]penicillanic acid (IIa).

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670328

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The Synthesis of cis- and trans- 7-Phenylkacetamido-O-2-isocephemO-2-Isocephems are alternatively called isooxacephems (1984)

Hakimelahi, Gholam Hosein

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 902-905

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The synthesis of the title compounds is described.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670331

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Digitale Medien

Erratum (1984)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 927-927

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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.19840670334

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17

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Absolute Conformation and Configuration of (2S, 3S)-3-Acetoxy-5-(dimethylaminoethyl)-2-(4-methoxyphenyl)-2,3-dihydro-1,5-benzothiazepin-4(5H)-one Chloride (Dilthiazem Hydrochloride) (1984)

Kojić-Prodić, Biserka ; Ružić-Toroš, ŽIva ; Šunjić, Vitomir ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 916-926

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Resolution of racemic cis-3-(2-aminophenylthio)-2-hydroxy-3-(4-methoxyphenyl) propionic acid (2) via the cinchonidine salt 3, and brucine salt 4, isolation of the calcium salts (+)- and (-)-5, as well as their cyclization to enantiomeric 1,5-benzothiazepines (+)- and (-)-1, are described. X-Ray single-crystal analysis reveals (2S, 3S) absolute configuration of (+)-1 on the basis of tentative comparison of CD data with those for the 1,4-benzodiazepine derivative (+)-8 of known absolute configuration.

Zusätzliches Material: 4 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670333

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Digitale Medien

Masthead (1984)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984)

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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.19840670401

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19

Digitale Medien

Synthese und Struktur von Zink-Komplexen von 2-Amino-1-azetinen (1984)

Stierli, Friedrich ; Prewo, Roland ; Bieri, Jost H. ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 927-933

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Synthesis ad Structure of Zinc Complexes of 2-Amino-1-azetinesThe 2-dimethylamino-3,3-dimethyl-1-azetines 7a and 7b have been synthesized in analogy to the procedure reported by Ghosez et al. [1] (Scheme). The crystal structure of 1-benzhydryl-azetidindimethyliminium chloride 5a, a precursor of azetine 7a, has been established by X-ray diffraction analysis. Treatment of azetines 7a and 7b with ZnBr2 in CH2Cl2/MeCN yielded tetrahedral bis (azetine)dibromozinc complexes 8a and 8b, respectively (Scheme 2). The molecular structure of 8a has been determined by X-ray diffraction analysis too.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670402

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Enantioselective synthesis of (+)- and (-)-cis-2-methyl-4-propyl-1,3-oxathiane and their olfactive properties (1984)

Pickenhagen, Wihelm ; Brönner-Schindler, Helene

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 947-952

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The enantioselective synthesis of (+)- and (-)-cis-2-methyl-4-propyl-1,3-oxathine 8 and 9 form (E)-2-hezen-1-ol (1) as common starting material is described. The two enantiomeric forms exhibit different organoleptic properties.

Zusätzliches Material: 2 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670405

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Aliphatic Liquid Crystals with Positive Dielectric Anisotropy (1984)

Osman, Maged A. ; Huynh-Ba, T.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 959-963

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Cyanothyl-subsituted cylohexyl cyclohexanoates, bi(cyclohexanes) and phenyl cyclohexanes were synthisized. Their mesmorphic behaviour is compared to that of the corresponding cyano derivatives. (Cyanoethyl)cyclohexyl cyclohenxanoates show mesmorphic properties in contrast to the corresponding cyano derivative. Separation of the cyano substituent from the rigid core of an anisotropic aliphatic compound by methylene groups enhances the thermodynamic stability of the mesophase. In aromatic compound, the cyanoethyl group leads to lower clearing points. These phenomena are attributed to teh influence of steric effects on the packing density and to the dependence of the clearing point on molecular association.

Zusätzliches Material: 2 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670407

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Monohaptenic Nα-Benzoyl-L-lysine Derivatives as Anaphylactogens: the Importance of the Unsubstituted Carboxyl Group (1984)

Guenin, Raymond ; Schneider, Conrad H.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1000-1002

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Nα-L-Iysine with a 2-carboxy-4, 6-dinitrophenyl (Dncp) haptenic group on the ε-amino function is a potent anaphylactogen in the guinea pig. We prepared Nε -Dncp- Nα-benzoly-L-Iysinamide and Nε-Dncp-Nα-benzoyl-L-lysyl-1-aminopropane where the carboxyl group of Iysine is blocked. Both compounds were non-elections of anaphylaxis.

Zusätzliches Material: 1 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670411

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C45- und C50-Carotinoide. 2. Mitteilung. Synthese von optisch aktiven acyclischen C15-Endgruppen (1984)

Kramer, Andreas ; Pfander, Hanspeter

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 21-28

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: C45- and C50-Carotenoids. Synthesis of Optically Active Acyclic C15-End GroupsThe optically active C15-end groups (S)-12, (S)-13 and (R)-14 were prepared from the C12-synthon (S)-11 in good chemical and optical yield. These C15-end groups are suitable compounds for the synthesis of optically active C45- and C50-carotenoids.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670104

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Interactions between Functional Groups. Part I. Crystal Structure of 2-Phenylethynyl-N,N-dimthlaniline at 98 K: A Remarkably Short C—H … C Distance (1984)

Wallis, John D. ; Dunitz, Jack D.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 39-46

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: In the crystal structure of the title compound at 98 K the dimethylamino group has pyramidal geometry. The nitrogenlone pair is not directed towards the triple bond; instead, one N—CH3 bond lies almost in the plane of the disubstituted ring, directed away from the triple bond, while the other N—CH3 bond and the lone pair are directed to opposite sides of the plane, nearer to the acetylene. There is a remarkably short intramolecular contact (2.39 Å) between a methyl H- and an acetylenic C-atom. The Taft σI parameter of the arylethynyl substituent appears to be similar to that of a carboxylic ester, judging from the bond-angle deformation at the ipso-C-atom.

Zusätzliches Material: 5 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670106

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Die Herzglykoside des Pfeilgiftes von Lophopetalum toxicum LOHER. 13. Mitteilung über Celastraceen-InhaltsstoffeAus der Dissertation von Helmut Habermeier, München, 1981. (1984)

Wagner, Hildebert ; Habermeier, Helmut ; Schulten, Hans-Rolf

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 54-64

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The Heart Glycosides of the Arrow Poison of Lophopetalum toxicum LOHERFrom the cytotoxic and positive inotropic acting bark extract of the Philippinan Lophopetalum toxicum eight heart glycosides have been isolated and their structures have been elucidated mainly by field-desorption-MS- and 1- and 13C-NMR spectroscopy. Besides the known k-Strophanthidin (1), Antiarigenin (6) and β-Antiarin (Antiarigenin-3-β-O-α-L-rhamnoside, 10) the following mono- and diglycosides could be identified: strophanthidin-3-β-O-α-6-desoxy-D-allopyranoside (strophalloside, 2), strophanthidin-3-β-O-β-6-desoxy-D-glucopyranoside (= Strophanthidin chinovoside, 3), strophanthidin-3-β-O[-4Oβ-D-allopyranosyl-β-6-desoxy-D-allopyranoside] (4), strophanthidin-3-β-O-[3-O-β-D-glucopyranosyl-β-6-desoxy-D-talopyranoside] (5), antiarigenin-3-β-O-[3-O-β-D-gulopyranosyl-β-6-desoxy-D-talopyranoside] (7), antiarigenin-3-β-O-[4O-β-D-allopyranosyl-β-6-desoxy-D-allopyranoside] (8), and antiarigenin-3-β-O-β-6-desoxy-D-allopyranoside (antiallosid) (9). The structure of strophanthidinchinovoside (3) could be confirmed by synthesis.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670108

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On the Structure of Oxirane Molecular Cation. Preliminary CommunicationDedicated to Prof. Christoph Tamm on the occasion of his 60th birthday (1984)

Bally, Thomas ; Nitsche, Stephan ; Haselbach, Edwin

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 86-90

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: A recent controversy on the interpretation of the ESR spectrum of ionized oxirane is clarified on the basis of the electronic absorption spectra of ionized tetramethyloxirane and 9,10-octalineoxide. The results favour a ring-opened structure for oxirane molecular cation, resulting from C—C bond cleavage and being iso-π-electronic to allyl radical.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670111

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Die Acylierung von Acetylenen mit β, γ-ungesättigten Säurechloriden. Eine neue Synthese von 5-CyclopentenonenTeilweise vorgetragen an der Versammlung der Schweizerischen Chemischen Gesellschaft am 15. Oktober 1982 in Bern; als vorläufige Mitteilung erschienen in [1]. (1984)

Karpf, Martin

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 73-85

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The Acylation of Acetylenes with β,γ-Unsaturated Acid Chlorides, A New Synthesis of 5-Substituted 2-CyclopentenonesThe acylation of acetylenes with α,α-disubstituted, β,γ-unsaturated acid chlorides under Friedel-Crafts-type conditions leads to 5-substituted 2-cyclopentenones. Phenols are formed with β,γ-unsaturated acid chlorides bearing at least one α-H-atom. These transformations are explained by the intramolecular cyclization of the initially formed vinyl cation, which, in the cases of α,α-disubstituted acid chlorides, is followed by ring contraction. The reaction leading to 2-cyclopentenones is applied to the synthesis of some spiro[4.4]nona- and spiro[4.5]deca-2,6-dienones.

Zusätzliches Material: 1 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670110

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Palladium-promoted Cyclization of Tetra-alkylated 1-Arylazonaphthalenes to 2-Aryl-benzo[g]indazoles (1984)

Hugentobler, Max ; Klaus, Alfred J. ; Ruppen, Peter ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 113-119

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: 1-Arylazonaphthalenes with all the potential cyclopalladation sites (one peri- and three ortho-positions) substituted by methyl or ethyl groups react with stoicheiometric or catalytic amounts of sodium tetrachloropalladate(II) to the corresponding 2-arylbenzo[g]indazoles. Possible mechanisms for the catalytic cyclization reaction are proposed.

Zusätzliches Material: 1 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670114

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Photochemical reactions. 132nd communication131st Communication, see [1]. Photochemistry of 5,6-epoxy-5,6-dihydro-7-methyl-β-ionine: Influence of a methyl group at the enone side chain on the oxirane cleavagePresented in Part by B. F. at the IXth IUPAC Symposium on Photochemistry, July 25-30 1982, Pau (France). (1984)

Siewnski, Antoni ; Henggeler, Barbara ; Wolf, Hans Richard ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 120-128

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: 1n, π*-Excitation of the γ,δ-epoxy-enone (E)-3 leads exclusively to the conformers (Z)-3A + B. On 1π, π*-excitation of (E)-3, in addition to (Z)-3A + B, products 6-9 arising from a carbene intermediate e are formed. However, products of an isomerization via C(γ), O-bond cleavage of the oxirane were not formed on either mode of excitation. On thermolysis, at 80° the conformer (Z)-3A is transformed into (Z)-3B, which on photolysis returns to (Z)-3A and (E)-3. At 160°, however, (Z)-3B rearranges to the isomers 6, 10 and 11.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670115

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Selective Photoinduced Oxidation of Benzylic Methylen Groups through UV Irradiation in Presence of Ferric Chloride (1984)

Barbier, Michel

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 866-869

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Selective oxidation of benzylic methylene groups through UV irradiation in acetone/water/FeCl3 mixtures is reported. This method applied to a series of model compounds, provides an easy access to the corresponding 1-oxo derivative. Thus, tetralin gives a 100% yield of 1-tetralone, indane leads to 60% of 1-indanone, and diphenylmethane is oxidized to benzophenone with 80% yield. However, under the same conditions, alkyl-substituted aromatic hydrocarbons such as toluene, ethyl- and propylbenzene lead to low yields of aldehydes or ketones. Isochromane furnishes a mixture of two substances which can be interconverted, namely the expected l-isochromanone (9%) and the corresponding hydroxy acid (23%). We failed to apply the method to nitrogen heterocycles containing benzylic groups such as 1,2,3,4- and 5,6,7,8-tetrahydroquinoline as they do not react due to the formation of complexes which precipitate from the solutions.

Zusätzliches Material: 1 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670327

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High performance liquid chromatography (HPLC) of natural products part VI.For part V, see [1] Sulfoxides of penicillin N and cephalosporin c and their role in biosynthesis of β-lactam antibiotics (1984)

Kukolja, S. ; Miller, R. D. ; Duckworth, D. C. ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 876-884

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Pure pencillin N α-sulfoxide (1) and penicillin N β-sulfoxide (2) were obtained by HPLC and tested as substrates for deacetoxycephalosporin C synthetase (DXCS). Neither one of the sulfoxides was utilized under conditions of conversion of penicillin N (8) to deacetoxycephalosporin C (9). The cephalosporin C α and β-sulfoxides (3 and 4, resp.) were also prepared. Relative stabilities of the sulfoxides 3 and 4 are discussed by interpretation of the 13C-NMR spectra.

Zusätzliches Material: 9 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670329

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Die Busseine C, D, E, F, G, H, J, K, L und M, zehn neue Tetranortriterpene aus Entandrophragma bussei Harms.Herrn Prof. D.A.H. Taylor, University of Natal, Durban, Natal, South Africa, danken wir bestens für die Überlassung von Extrakten. (1984)

Guex, Matthias ; Tamm, Christoph

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 885-901

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The Business C,D,E,F,G,H,J,K,L und M, Ten New Tetranortriterpenes from Entandrophragma Bussei HarmsTen new tetranortriterpenes, busseins C, D, E, F, G., H, J, K, L and M have been isolated from the petroleum ether extract of the timber of Entandrophragma bussei Harms. utilizing separation by high-pressure liquid chromatography (HPLC). The structural assignments are based mainly on spectral evidence. For the 1H-NMR spectroscopy extensive use of nuclear Overhauser effects (NOE) was made.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670330

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Mitteilungen-Communiacations (1984)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 928-930

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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.19840670335

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The Synthesis and Application of Novel Nitrating and Nitrosating AgentsWork supported by the Shiraz University Research Council. (1984)

Hakimalahi, Gholam H. ; Sharghi, Hashem ; Zarrinmayeh, Hamide ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 906-915

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Alcohols and phenols are efficiently nitrated with thionyl chloride nitrate or thionyl nitrate, even in the presence of an aromatic moiety. While thionyl chloride nitrate is suitable for nitration of primary OH-groups in carbohydrates, thionyl nitrate is reactive enough to react with secondary OH-groups as well. These reagents permit the highly selective nitration of the 5′-,2′5′- and 3′, 5′-OH-groups of ribonucleosides to produce either mono-or diprotected nitro derivatives in high yields. Carbon acids and the enol form of some ketones are efficiently nitrated with trifluoromethanesulfonyl nitrate/potassium tert-butoxide. Lutidine N-oxide (2,6-(CH3)2C5H3N O) was found to have a marked effect on nitration reactions. Similarly, thionyl chloride nitrite and thionyl nitrite exhibit an excellent capacity for nitrosation of the aforementioned substrates.

Zusätzliches Material: 5 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670332

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Radical Ions of Conjugated Polycyclic Hydrocarbons Containing Two Phenalenyl π-Systems (1984)

Gerson, Fabin ; Knöbel, Jürgen ; Metzger, André ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 934-938

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The radical cations and the radical of 1,2-bis(phenalen-1-ylidene)ethane (1), 1,2-bis(phenalen-1-ylidene)ethene (2) and pentaleno[1,2,3-cd: 4,5,6-c′ d′]diphenalene (3) have been characterized by ESR and ENDOR spectroscopy. The ease of formation of these radical ions and their π-spin distributions are interpreted in terms of a simple model correlates the frontier orbitals of 1, 2 and 3 with the nonbonding MO's of two phenalenyl π-systems.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670403

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The Synthesis and Reactions of 1-(2-Propynyl)pyidinium Salts (1984)

Katritzky, Alan R. ; Schwarz, Otto A. ; Rubio, Olga ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 939-946

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The synthesis of 1-(2-propynyl)pyridinium salts 3 described. Compounds 3 react with a second pyridine molecule, in the presence of the corresponding hydrochloride, to form products of type 4, Certain bases cause the 1-(2-propynyl)pyridinium salts 3 to rearrange into 1-propadienylpyridinium salts. 5. Diethylamine converts compounds 3 into 1-acetonylpyridinium salts 8. Moreover, treatment of 3 or 5 with sodium methoxide gives enol ether sof type 9, which can be hydrolyzed to teh ketones 8. Addition of bromine to some of teh unsaturated compounds is also reported.

Zusätzliches Material: 5 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670404

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HNO, an Intermediate in (Light-induced) Rearrangement Reactions of Nitrosooxy Compounds and Nitrosamines (1984)

Müller, René-Pierre ; Murata, Shigeo ; Nonella, Marco ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 953-958

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: IR-spectroscopic investigations of light-induced rearrangement reactions of nitrosooxymethane (CH3ONO3), nitrosooxyethane (CH3CH2ONO) and N,N-dimethylnitrosamine ((CH3)2NNO) in low-temperature rare-gas matrices have established that these molecules are transformed in two photolysis steps to the previously unknown C-nitroso compounds nitrosomethanol (CH2(OH)(NO)), 1-nitrosoethanol (CH3CH(OH)(NO)), and methyl(nitrosomethyl)amine CH2(NO)(NH)(CH3). Evidence for a similar rearrangement reaction has been advanced for N-Nitrosopyrrolidine which is converted to C-nitrosopyrrolidine . The matrix-isolation technique in combination with wavelength-selective irradiation allowed to trap and characterize an intermediate of rearrangement which revealed to be nitroxyl (HNO) complex (CH2…HNO, CH3CHO…HNO, CH3N = CH2…HNO, and ). Since these findings have a close resemblance with rearrangement reactions of more complex nitrosooxy compounds, nitrosamines, or nitrosohydrazines used in organic synthesis, it is suggested that also in these reactions nitroxyl is present as an intermediate species.

Zusätzliches Material: 3 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670406

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1,2-Epoxycarotinoide. 3. Mitteilung. Isolierun von 1,2-Epoxy-1,2-dihydrolycopin aus Tomaten (1984)

Berset, Daniel ; Pafander, Hansperter

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 964-967

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: 1,2-Epoxycarotenoids: Isolation of 1,2-Epoxy-1,2-dihydrolycopene from TomatoesThe optically active, 1,2-epoxy-1,2-dihydrolycopene was isolated from tomatoes. Its constitution was established by comparison with the racemic synthetic compound.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670408

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1,2-Epoxycarotinoide. 4. Mitteilung. Synthese, 1H-NMR- und CD-Studien von (S)-1,2-Epoxy-1,2-dihydrolycopin und (S)-1′,2′-Epoxy-1′,2′-dihydro-γ-carotin (1984)

Kamber, Matthias ; Pfander, Hanspeter ; Noack, Klaus

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 968-985

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Schlagwort(e): Chemistry ; Organic Chemistry

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Thema: Chemie und Pharmazie

Notizen: 1,2-Epoxycarotenoids: Synthesis, 1H-NMR and CD Studies of (S)-1,2-Epoxy-1,2-dihydrolycopene and (S)-1′,2′-Epoxy-1′, 2′ -dihydro-γ-caroteneThe synthesis of (S)-1,2-epoxy-1,2-dihydrolycopene ((S)-1) and (S)-1′, 2′ -epoxy- 1′, 2′ -dihydro-γ-carotene ((S)-2) are described. The CD spectra of the (all-E)-isomers and of the isomers (7Z, S)-1 and (7′Z, S)-2 are discussed. The comparison of the CD spectra of the synthetic (S)-1 and the compound isolated from the tomatoes proves the (S)-configuration of the natural product.

Zusätzliches Material: 9 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670409

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Plectranthone A, B, C und D. Diterpenoide Phenanthren-1,4-dione aus Blattdrüsen einer Plectranthuus sp. (Labiatae) (1984)

Alder, Alfredo Carlos ; Rüedi, Peter ; Eugster, Conrad Hans

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1003-1011

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Plectranthons A, B, C, and D. Diterpenoid Phenanthrene-1,4-diones from Leaf-glands a Plectranthus sp. (Labiatae)The following structures of four new 1,4-phenanthraquionones, isolated in minute amounts from the coloured leaf-glands of a Plectranthus sp. obtained from the borders of Lake Kiwu2, Rwanda, are proposed: plectranthon A (1; 3-hydroxy-5, 7,8-trimethyl-2-(2-propenyl)phenanthrene-1, 4-dione), plectranthon B (2; 2-(2ξ-acetoxypropyl)-3-hydroxy-5,7,8-trimethylphenanthrene-1,4-dione), plextranthon C (3; 3-hydroxy- 7,8-diemethyl-2-(2-propenyl)phenanthrene-1,4-dione), and plectranthon D (4; 3-hydroxy-7,8,10-trimethyl-2-(2-propenyl)phenanthrene-1,4-dione). 2-(2ξ-Hydroxypropyl)-3,6-dihydroxy-5,7,8-trimethylphenanthrene-1,4-dione (11), a compound very similar to 1-4, was prepared by a Wagner-Meerwein, rearrangement of coleon E (5). Biogenetically, the plectranthons are derived from abietanoic precursors. The compounds 1, 2 and 4 are the first natural C20-phenanthrenes of diterpenoid origin.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670412

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Stereoselective Control in the Base-Catalyzed H/D Exchange of 5,6-Dimethylidene-2-bicyclo[2.2.n]alkanone Tricarbonyliron Complexes. Revision of the Structures of Tricarbonyliron Complexes of 5,6-Dimethylidenebicyclo[2.2.2]oct-2-ene and 5,6-Dimethylidenebicyclo[2.2.1]hept-2-eneA preliminary communication was presented at the Autumn Meeting of the Swiss Chemical Society, Bern, October 14, 1983. (1984)

Barras, Charls A. ; Roulet, Rymond ; Carrupt, Pierre-Alain ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 986-999

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Oxidative hydroboration of exo- (1) and end-Fe(CO)3 (2) complexes of 5,6-dimethylidenebicyclo[2.2.2]oct-2-ene are highly stereoselective and give endo -alcohol 3 and exo -alcohol 4 as major products, respectively, Collins oxidations of 3 and 4 furnish the corresponding exo -Fe(CO)3 -complexed 5,6-dimethylidene-2-bicyclo-[2.2.2]octanone 7 and 8. NaBH4 reduction of exo-complexes 7 gives a mixture of 3 and isomeric exo-alcohol 18, whereas reduction of endo-complexes 8 gives the endo-alcohol, endo-complexes 19, as the sole product. The base-catalyzed H/D exchange of 7 and 8 afford the dideuterated exo-complex 35 and the monodeuterated endo-complex 32, respectively. Oxidative hydroborations of the exo-(9) and endo-Fe(CO)3 (10) complexes of 5,6-dimethylidenebicyclo[2.2.1]hept-2-ene give the corresponding exo-alcohols 39 and 40. Oxidation of 39 and 40 gives the exo- and endo-complexes 41 and 42, respectively, of 5,6-dimethylidene-2-bicyclo[2.2.]heptanone. Only Hexo —C(3) can be exchanged in 42, wheres both H-atoms at C(3) in 41 are exchangeable. The endo-Fe(CO)3 group in 8 and 42 blocks the base-catalyzed H/D exchange of Hendo —C(3), thus providing a test for the configuration of Fe(CO)3 group in these systems. These studies have led to a revision of the iron configurations proposed by Hansen et al, [2] for 1, 2, 9 and 10.

Zusätzliches Material: 1 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670410

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Mitteilungen - Communications (1984)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 361-364

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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.19840670143

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Parallelism Between Nucleophilically Solvent-Assisted and Phenyl-Assisted Reactions. Possible Existence of Nucleophilically β-Phenyl-Solvated Ion Pairs (1984)

Laureillard, Jeane ; Casadevall, André ; Casadevall, Eliette

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 352-360

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Solvolysis rate constants in MeOH and t-BuOh are compared for β-methyl and β-phenyl derivatives of two cycloakyl systems. It appears that the β-phenyl derivatives solvolyse at te same rate as the β-methyl ones. The lack of deceleration is attributed to phenyl assistance. It is established by configurational analysis of the reaction products, that those products which necessarily originate from a cationic species are the most abundant ones. It is suggested that these reactions could proceed through ion-pair intermediates, which are nucleophilically solvated by phelyl or by the solvent. A parallel between phenyl assistance and ‘SN2 (intermediate)’ mechanism, suggested by Bentely & Schleyer, is drawn.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670142

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Percolative Phenomena in Microemulsions of the ‘One-Component Macrofluid’ Type (1984)

Eicke, Hans-Friedrich ; Hilfiker, Rolf ; Holz, Manfred

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 361-372

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The temperature dependence of the water self-diffusion coefficients (D), as well as those of low- and high-field (stationary and time-dependent) specific conductivities (K), have been determined in the percolation regime of ternary mixtures of water, AOT, and oil. For the first time a pronounced similarity in the behavior of D and κ was detected giving instructive hints about the large variations in the specific conductivities of these systems. Results from kinetic and stationary experiments are consistent with a network-structure model of micro phases in the percolation regime in which the micro phases retain their discrete character.

Zusätzliches Material: 8 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670202

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Synthèse facile de dérivés du diphényl-2,4-aza-3-bicyclo[3.3.1]nonane et du diphényl-7,8-aza-8-bicyclo[4.3.1]décaneUne partie de ce travail a fait l'object d'une communication préliminaire [1]. (1984)

Campo, Carmen Del ; Martinez, Ernesto ; Trigo, Gregorio G.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1291-1297

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Facile synthesis of derivatives of 2,4-diphenyl-3-azabicyclo[3.3.1]nonane and 7,9-diphenyl-8-azabicyclo[4.3.1]decaneThe facile synthesis of hydantoins, cyanhydrins and aminonitriles derived from 2,4-diphenyl-3-azabicyclo[3.3.1]nonanone and 7,9-diphenyl-8-azabicyclo[4.3.1]decanone is described. Configurations at C(9) or C(10) of the new compounds wth pharmaceutical and synthetical utility is deduced from their spectral properties.

Zusätzliches Material: 4 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670515

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Fragmentation of 6-Deoxy-6-halo-hexono-1,5-ortholactones: A Concerted, Nonstereospecific Process (1984)

Bernet, Bruno ; Vasella, Andrea

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1328-1347

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The synthesis of the D-arabino- and D-ribo-ortholactones 13a-f and 15b-f and their treatment with Zn leading to the unsaturated esters 14a-d and 16a-d are described. Possible fragmentation mechanisms are discussed. The results were only compatible wit a concerted, nonsynchronous process, where both the axial lone pair of the ring oxygen atom and the lone pair formed during rupture of the C(5), O-bond participate in the elimination of the axial and of the equatorial C(1)-alkoxy groups, respectively.

Zusätzliches Material: 4 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670519

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Electron-Transfer-Induced Conformational Changes. The Example of 1,8-Dimethyl[14]annulene (1984)

Huber, Walter

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1368-1373

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: This communication reports ESR-spectroscopic investigations of the radical anion of 1,8-dimethyl[14]annulene (1) which possesses a flexible molecular framework allowing configurational and conformational mobility. The ESR and ENDOR spectra indicate that at higher temperatures (T 〉 160 K), \documentclass{article}\pagestyle{empty}\begin{document}$ 1^{- \atop \dot{}} $\end{document} exists as a mixture of several distinct isomers. One of them, the sole product at T 〈 160 K, is found to be energetically preferred. The configuration and the conformation of this species can be determined by interpretation of the hyperfine data in terms of a singly occupied MO of the 14-membered π-perimeter.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670523

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Dimers of 3,7-dehydrotroponesFor this nomenclature, see [1a]. (bicyclo[3.2.0]hepta-1(7),2,4-trien-6-ones) (1984)

Szechner, Barbara ; Rey, Max ; Dreiding, André S. ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1386-1396

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: 2-(tert-Butyl)-3,7-dehydrotropone (7-(tert-butyl)bicyclo[3.2.0]hepta-1(7),2,4-trien-6-one; 1) was found to dimerize reversibly to 2A by [2 + 4]-cycloaddition/cycloreversion reaction. The equilibrium lies on the side of the highly strained dimer 2A in the solid state, and on the side of the monomer 1 in solution. The [2 + 4]-reaction is fully perisite-, regio- and stereoselective. Above room temperature, 1 irreversibly formed a decarbonylated dimer 6, probably via the intermediate 9A or 9B, which resulted either from a dimerisation of 1 by [4 + 6]-cycloaddition or from a sigmatropic rearrangement of the originally formed dimer 2A or 2B. Similary, the 6-bromo derivative 14 afforded the corresponding decarbonylated dimer 15. Should the formation of 6 and 15 be due to a primary cycloaddition then that reaction is fully peri-, site- and regioselective. Mild LiAlH4-reduction of 6 and subsequent acetylation yielded the acetate 11, the structure of which was established by an X-ray analysis. More vigorous LiAlH4-treatment also reduced the terminal fulvenoid double bond of 6 and acetylation of the crude product led to the acetated 12 and 13.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670526

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Mitteilungen - Communications (1984)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1427-1428

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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.19840670530

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Elektromotorisches Verhalten von Flüssigmembranelektroden-Messketten mit enantiomerenselektiven chiralen Ionophoren (1984)

Morf, Werner E. ; Bussmann, Walter ; Simon, Wilhelm

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1427-1438

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Electromotive Behaviour of Liquid-membrane Electrode Assemblies Based on Enantiomer-selective Chiral IonophoresA comprehensive theoretical treatment is given for the potentiometric behavior of enantiomer-selective membrane electrodes based on chiral ionophores and plasticizers. The membrane model allows for free and complexed enantiomeric or racemic ions (e.g. ephedronium and l-phenylethylammonium ions) as well as for achiral interfering ions. Experiments are derived for the determination of the stoichiometry and the relative stability of enantiomeric ion/enantiomeric ligand complexes, and for the analytical measurement of the enantiomeric excess of ions in solution.

Zusätzliches Material: 5 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670602

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Water-Exchange Mechanism of Tetraaquapalladium(II). A Variable-Pressure and Variable-Temperature Oxygen-17 NMR StudyPart 23 of the series ‘High-Pressure NMR Kinetics’. For part 22, see [1]. (1984)

Helm, Lothar ; Elding, Lars I. ; Merbach, André E.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1453-1460

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Water exchange of square-planar Pd(H2O)24+ has been studied as a function of temperature (240 to 345 K) and pressure (0.1 to 260 MPa, at 324 K) by measuring the 17/O-FT-NMR line-widths of the resonance from coordinated water at 27.11 and 48.78 MHz. The following exchange parameters were obtained: k298ex = (560 ± 40) s-1, ΔH* = (49.5 ± 1.9) kJ mol-1, ΔS* = - (26 ± 6) J K-1 mol-1 and ΔV* = - (2.2 ± 0.2) cm3 mol-1. The values refere to an aqueous perchlorate medium with an ionic strength between 2.0 and 2.6 m and a perchloric-acid concentration between 0.8 and 1.7 m, and are interpreted in terms of an associative (a) activation for the exchange. The exchange rate for Pd(H2O)24+ is 1.4 × 106 times faster than for Pt(H2O)24+ at 298 K. A comparison with reactions between other nucleophiles and Pd(H2O)24+ is also made.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670605

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Etudes sur les composés organométalliques partie XXPartie XIX, v. [5]. Sélectivité de l'addition 1,4 de composés benzyliques du titane IV avec la benzylidéneacétone (1984)

Roulet, Daniel ; Capéros, José ; Jacot-Guillarmod, André

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1475-1477

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Studies of Organometallic Compounds, XX. Selectivity of 1,4-Addition of Benzyltitanium Compounds with BenzylildenacetoneTetrabenzyltitanium and dialkoxydibenzyltitanium compounds give essentially 1,4- addition with trans-4-phenyl-3-buten-2-one.

Zusätzliches Material: 1 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670608

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Aminierende, reduktive Kupplung aromatischer Aldehyde mit Tris(dialkylamino)methylvanandium (IV) zu N,N,N′,N′-Tetraaalkyl-1,2-diaryläthylendiaminen (1984)

Imwinkelried, René ; Seebach, Dieter

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1496-1502

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Schlagwort(e): Chemistry ; Organic Chemistry

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Notizen: Aminative Reductive Coupling of Aromatic Aldehydes to N,N,N′,N′-Tetraalkyl-1,2-diarylethylenediamines, Induced by Tris(dialkylamino)methylvanadium (IV)In a novel type of reaction, certain aromatic aldehydes (benzaldehyde, p-methoxybenzaldehyde, 1-naphthaldehyde, furan-2-carbaldehyde) and secondary amines are coupled to give N,N,N′,N′-tetraalkyl-1,2-diarylethylenediamines 1-6. The reagents are tris(dialkylamino)methylvanadium(IV) compounds (cf. Eqn. 2). These are generated in situ either from isolable chlorotris(dialkylamino) vanadium(IV) (Eqn. 3), or preferably, from an Et2O/pentane solution of VCl4 which is treated sequentially with 3 equiv. of lithium dialkylamide, 1 equiv. of MeLi, and 0.8 equiv. of an aromatic aldehyde, to give the products 1-6 in a one-pot preparation (Scheme 2). The yields range from 14 to 54%. The diastereoisomeric mixtures (meso- and (±)-forms) obtained are separated by chromatography (Al2O3, petroleum ether/Et2O/Et3N), and the pure stereoisomers fully characterized. A mechanism of the reductive coupling induced by CH3V (NR2)3 is proposed (Scheme 1).

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670612

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Functionalized Cycloheptanes from Bicyclo[4.2.1]nonanes (1984)

Huston, Rima ; Rey, Max ; Dreiding, André S.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1506-1514

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Several oxidative, reductive and C,C-cleavage reactions were performed starting from the three bicyclo[4.2.1]nona-3,7-diene-2-one derivatives 1, 5 and 18. The oxidations were selective and led to the diols 2,8 and 9, and the epoxides 6,9, and 20. The reductions were selective only in the case of 20 21; otherwise they led to mixtures of the alcohols 10 and 11, and of the dienes 14 and 15. The periodate ring cleavages afforded the functionalized cycloheptane derivatives 3, 12, 13 and 16. Configurational assignments were made on the basis of detailed 1H-NMR and X-ray analysis of 20.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670614

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Drüsenfarbstoffe aus tropischen Labiaten: Parviflorone aus Plectranthus strigosus BENTH. (1984)

Alder, Aldredo Carlos ; Rüdi, Peter ; Eugster, Conrad Hans

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1531-1534

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Red-Coloured Abietanoids from Leaf-Glands of Plectranthus strigosus BENTH.Chromatographic examination of the red-coloured diterpenoids from the South-African title plant yielded the following compounds: parviflorone A(1), parviflorone B (2), parviflorone C(3), parviflorone E (4) parviflorone D (5), parviflorone F (6), parviflorone G (7), and parviflorone H (8). Compounds 7 and 8 represent new variants of these quinone methides.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670617

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Drüsenfarbstoffe aus Labiaten: Die polaren Diterpenoide aus Plectranthus argentatus S. T. BLAKEVorangehende Arbeiten s. [1] [2] und darin zitierte frühere Publikationen. (1984)

Alder, Alfredo Carlos ; Rüdi, Peter ; Eugster, Hans

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1523-1530

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Polar Diterpenoids from Leaf-Glands of Plectranthus argentatus S. T. BLAKEFrom the red leaf-glands of the Australian Plectranthus argentatus the following novel diterpenoids were isolated: coleon-U-quinone (1), 8α,9α-epoxycoleon-U-quinone (3), 6β-formyloxy-7α-hydroxyroyleanone (7), and 5,6-dihydrocoleon U (10), besides the already known compounds 6β, 7α-dihydroxyroyleanone (4), 7α-acetoxy-6β-hydroxyroyleanone (5), and 7α-formyloxy-6β-hydroxyroyleanone (6). Epoxydation of 1 by perborate led in 32% yield to the epoxyquinone 3.

Zusätzliches Material: 4 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670616

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Deoxy-nitrosugars 8th communication7th Communication: [1]. Convenient preparation of 1-C-nitroglycosyl chlorides. Halonitro ethers from hydroxy oximes (1984)

Meuwly, Roger ; Vasella, Andrea

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1568-1571

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Partially protected 4- or 5-hydroxy-sugar oximes were transformed into 5- or 6-membered 1-C-nitroglycosyl chlorides, respectively, by reaction with NaOCl under phase-transfer conditions. With the exception of the oxidation of the gluco-derivative 1 giving the anomers 6 and 7, the reactions were completely diastereoselective.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670622

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The synthesis and transition temperatures of benzoate ester derivatives of 2-fluoro-4-hydroxy-and 3-fluoro-4-hydroxybenzonitriles (1984)

Kelly, Stephen M.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1572-1579

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The synthesis and the liquid-crystal temperatures of sixty 4-cyano-2-fluorophenyl and 4-cyano-3-fluorophylen 4-substituted benzoates are described. The nematic-isotropic liquid transition temperatures of the most of these novel esters are only marginally lower than those of the corresponding esters containing an H-atom in place of the F-substituent. In several instances, the clearing points of the F-substiuted-phenyl esters are higher than those of the non-substituted-phenyl esters. The nematic ranges of several of the new esters are markedly broader than those of the analogous non-F-substituted-phenyl esters.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670623

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An Example of Head-to-Head Dimerization of β4.4-Helices (1984)

Lorenzi, Gian Paolo ; Muri-Valle, Valentina ; Bangerter, Felix

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1588-1592

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: 1H-NMR and vapor-pressure osmometry results are presented, which indicate the occurrence of a rapid equilibrium involving the head-to-head dimerization of β44-helices in chloroform solutions of HCO-L-Ile-(D-AIle-L-Ile)4-OMe. This equilibrium typifies the one that, in Urry's view, would be responsible for the formation and breaking down of the ion-conducting channels formed by gramicidin A in lipid bilayers.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670625

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The synthesis and transition temperatures of ester derivatives of 2-fluoro-4-hydroxy- and 3-fluoro-4-hydroxybenzonitriles also incorporating aliphatic ring systems (1984)

Kelly, Stephen M. ; Schad, Hanspeter

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1580-1587

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The synthesis and liquid-crystal transition temperatures of forty ester derivatives of 2-fluoro-4-hydroxybenzonitrile and 3-fluoro-4-hydroxybenzonitrile are reported. The esters contain the trans-1,4-disubstituted cyclohexane or the 1,4-disubstituted bicyclo[2.2.2]octane rings (some contain an additional phenyl ring). Many of the novel F-substituted esters exhibit substantially higher nematic-isotropic transition temperatures than the corresponding unsubstituted esters. The order of clearing points of these laterally substiuted esters differing only in the presence of a benzene ring and the above-mentioned rings id established.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670624

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Synthese von neuen Morphin-Teilstrukturen des Typs 15,16-Secomorphinan (1984)

Révész, László

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1598-1602

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Synthesis of New Morphine Partial Structure 15,16-SecomorphinanThe synthesis of a new morphine partial structure, 15,16-secomorphinan, is described. One of the series, (±)-15, 16-secocyclorphan (5), has the analgesic potency of morphine and exhibits good binding to the opiate receptor.

Zusätzliches Material: 1 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670627

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Diastereoselektive synthese neuartiger Mannich-BasenAusführliche Übersichten über die klassische Mannich-Reaktion: [1-4]. mittels titanderivatenÜbersichtsartikel über die Verwendung von Organotitanverbindungen in der organischen Synthese: [5-8]., vorläufige mitteilung (1984)

Seebach, Dieter ; Betschart, Clauida ; Schiess, Martin

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1593-1597

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Diastereoselective Synthesis of Novel Mannich (Bases1) through Titanium ReagentsTrichlorotitanium dialkylamino-alkoxides (2; titanates of N, O-hemiacetals) are generated either from the corresponding lithium alkoxides and titanium tetrachloride (Scheme 1) or by addition of trichloro-dialkuylamino-titanium to aldehydes. The electrophilic (dialkylamino) alkylating reagents 2 are used to convert lithium enolates to β-dialkylamino-ketones and -esters 5 (Mannich bases), see Scheme 2 and Table. One diastereoisomer of the products 5g-5p thus obtained with cyclohexenolate is formed preferentially (66-84%). The configuration of the products of this first diastereoselective version of the Mannich reaction could not yet be determined. A typical procedure for carrying out the reaction is given.

Zusätzliches Material: 1 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670626

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63

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Optical resolution of 7-oxabicyclo[2.2.1]hept-21-ene derivatives. Diastereoselectivity in the formation of cyanohydrine-brucine complexes (1984)

Black, Kersey A. ; Vogel, Pierre

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1612-1615

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: A new, practical method for the optical resolution of bicyclic ketones if illusttrated by the preparation of (+)-(1R,4R)-7-oxabicyclo[2.2.1]bept-5-en-2-one ((+)-1) and (+)-(1R, 2S,4R)-2-cyano-7-oxabicyclo[2.2.1]hept-5-en-2-yul acetate ((+)-4). It involves the diastereoselective formation of a brucine complex with the corresponding cyanhydrine mixture.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670629

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Transition metal complexes with bidentate ligands spanning trans-positions part XVPart XIV: See [1]. X-ray structural and 31P-NMR solution studies of some three-coordinate silver complexes of 2,11-bis[di(tert-butyl)phosphinomethyl]benzo[c]phenathrene and related ligands (1984)

Camalli, Merceds ; Caruso, Francesco ; Chaloupka, Stanislav ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1603-1611

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: A series of three-coordinate bis(dialkylphosphinomethyl)benzo[c]phenanthrene Ag(I) complexes, alkyl= t-Bu, (1b), and cyclohexyl, (1c), anion = BF4, CIO4, CIO4, NO3, Cl, Br, I, have been prepared and thier 31P-NMR characteristics recorded. The solid state structures of [Ag(1b)Br], [Ag(1b)Cl] and [Ag(1b)CIO4] have been determined by X-ray diffraction. The Ag atom in these complexes shows distorted trigonal geometry. Selected bond lengths and angles are as follows: Ag-P = 2.463(4) Å and 2.433(5) Å, P-Ag-P=141.6(2)° in the bromo complex, Ag-P = 2.457(2) Å and 2.427(2) Å, P-Ag-P = 142.6(1)° ion the chloro complex, and Ag-P = 2.394(2) and 2.393 (2) Å, P-AG-P = 161.5(1)° in the perchlorato complex.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670628

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Further Syntheses of Optically Active Verrucarinic Acid, 43rd Communication of Verrucarins and Roridins42nd Commun. : [1]. (1984)

Grossen, Peter ; Herold, Peter ; Mohr, Peter ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1625-1629

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Two new syntheses of verrucarinic acid (2S, 3R-dihydroxy-3-methylpentanoic acid) and its derivatives, suitably protected for the further conversion to macrocyclic trichothecenes, are described. The first one makes use of a diastereoselective alkylation of a (-)-(S)-malic acid ester and the regioselective reductin of one carboxyl function toa methyl group. The second approach involves a stereoselective addition of an allylsilane to a chiral glyoxylate.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670631

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Steuerung der katalytischen Pyridinsynthese aus Alkien and Nitrilien durch (η6-Borinato)-Liganden am CobaltHerrn Prof. Dr. R. Köster, Mülheim a. d. Ruhr, mit herzlichen Wünschen zum 60. Geburtstag gewidmet (1984)

Bönnemann, Helmut ; Brijoux, Werner ; Brinkmann, Rainer ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1616-1624

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Control of the Catalytic Synthesis of Pyridine from Alkynes and Nitriles by the (η6-Borinato)-Nigands at Cobaltη6-Borinato groups as ligands at cobalt have unique effects on the chemo- and negioselectivity of the catalytic co-cyclization of alkynes and nitriles. The turnover number of the conversion of acrylonitrile and acetylene to give 2-vinylpyridine is considerably enhanced. Cyano compounds wih polar substitutents such as amino or thio groups can also be reacted. The homogeneous reaction of HCN with acetylene giving pyridine has been achieved for the first time.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670630

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Chemo- and Stereoselective Coordination of 5,6-Dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene by d8- and d6-Metal Carbonyls. Diels-Alder reactivity of Dienes Perturbed by Remote Olefin Complexation (1984)

Vioget, Philippe ; Bonivento, Massimiliano ; Roulet, Raymond ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1630-1637

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The endocyclic double bond C(2), C(3) in 5,6-dimethylidene-7-oxabicyclo[2.2.1]-hept-2-ene (1) can he coordinated selectively on its exo-face before complexation of the exocyclic s-cis-butadiene moiety. Irradiation of Ru3(CO)12 or Os3(CO)12 in the presence of 1 gave tetracarbonyl [(1R,2R, 3S,4S)-2,3-η-(5,6-dimethylidene-7-oxabicyclo[2.2.1]-hept-2-ene)]ruthenium (6) or -osmium (8). Similarly, irradiation of Cr(CO)6 or W(CO)6 in the presence of 1 gave pentacarbonyl[(1R, 2R, 3S,4S)-2,3-η-(5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene)]chromium (10) or -tungsten (11). Irradiation of complexes 6 and 11 in the presence of 1 led to further CO substitution giving bed-tricarbonyl-ae-bis[(1R,2R,3S,4S)-2,3-η-(5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene)]ruthenium (7) and trans-tetracarbonyl[(1R,2R,3S,4S)-2,3-η-(5,6-dimethylidene-7-oxabicyclo-[2.2.1]hept-2-ene)]tungsten (12), respectively. The diosmacyclobutane derivative cis-m̈-[(1R,3R,3S,4S)-(5,6-dimethylidene-7-oxabicyclo[2.2.1]hepta-2,3-diyl)]bis(tetracarbonyl-osmium) (Os-Os) (9) wa also obtained. The Diels-Alder reactivity of the exocyclic s-cis-butadiene moiety in complexs 7 and 8 was found to be significantly higher than that of the free triene 1.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670632

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Monoolefin and Diene Cycloaddition Induced by Transition-Metal Carbonyls. Cyclodimerization of 5,6-Dimethylidene-7-oxabicyclo[2.21]hept-2-ene Catalyzed by Dodecacarbonyltriosmium (1984)

Vioget, Philippe ; Bonivento, Massimiliano ; Roulet, Raymond ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1638-1646

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The products generated by heating 5,6-dimethylidene-7-oxabicyclo[2.2.1]hept-2-ene (1) with Fe2(CO)9, Ru3(CO)12, Os3(CO)12, Cr(CO)3(MeCN)3, (or W(CO)5(MeCN) or by treatment with Fe-atoms have been characterized by spectroscopic methods. Apart from the expected η2- and η4-complexes of the triene 1, condensation products are formed which arise from the formal [4 + 2]-cyclodimerization of 1 involving the endocyclic double bond of one molecule and the diene moiety of a second. The [4 + 2]-cyclodimerization is catalyzed by Os3(CO)12 in MeOH and gives 1,4-epoxy-7-methoxy-2,3-dimethylidene-1,2,3,4,4a,9,9a,10-octahydroanthracene (15)). Fe-Atoms induce a stereoselective [2 + 2]-cyclodimerization pf 1 which involves its endocyclic double bond and produces the dimer 8.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670633

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Synthese von 2,3-unsubstituierten, N-acylierten Indolen durch sigmatrope[3,3]-Umlagerung von O-Vinyl-N-phenylhydroxylaminderivaten (1984)

Martin, Pierre

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1647-1649

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Synthesis of 2,3-Unsubstituted N-Acylindoles by [3,3]-Rearrangement of the N-Phenyl-O-vinylhydroxylamine DerivativesSummary, Treatment of N-phenylhydroxamic acids with vinylacetate in the presence of Li2PdCl4 affords 2,3-unsubstituted N-acylindoles via hetero-Cope-rearrangement of the intermediate N-O-vinylhydroxylamine derivatives.

Zusätzliches Material: 1 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670634

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Mitteilugen - Communications (1984)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1669-1669

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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.19840670637

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Masthead (1984)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984)

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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.19840670701

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Photoreaction of (RS,SR)-3-Phenyl-6-hepten-2-ol. Benzene-Olefin Cycloadditions as a Synthetic Route to [5.5.5.5] Fenestranes. Part IIIFor part II of the series ‘Planarization of Tetracoordinate Carbon Atom’, see [1b]. (1984)

Mani, Jürg ; Cho, Jung-Hyuck ; Astik, Rameshchandra R. ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1930-1941

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Irradiation of (RS,SR)-3-Phenyl-6-hepten-2-ol (3n) gave the photoproducts 6n-10n. Some reactions of 6n and 8n are reported. The regio- and diastereoselectivity observed in the photoreaction of substituted 5-phenylpentenes is discussed with respect to conformational preferences of the compounds to be irradiated.

Zusätzliches Material: 1 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670731

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Benz[cd]indoles. Part III. A New Stereospecific Synthesis of Dihydrolysergic Acid and an Entry to 14-Substituted DerivativesPart of this work has been presented at the ‘Herbstversammlung der Schweizerischen Chemischen Gesellschaft’ at Berne, on October 18, 1982. (1984)

Haefliger, Walter E.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1942-1951

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: A new convenient synthesis of dihydrolysergic acid is described, which allows the preparation of substituted derivatives, especially those with different substitutents in the aromatic ring. Starting from appropriately substituted 5-nitro-2-tetralones, the synthesis leads via a tricyclic isonitrile to the indole-ring closure as the last step, thus circumventing the troublesome protection/deprotection of the latter.

Zusätzliches Material: 1 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670732

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Triaziridines. Part IIIPart II, see [1].. Triaziridine, azimine, and triazene: A SCF study of the energy and structure of N3H3-isomers (1984)

Nguyen, Minh-Tho ; Kaneti, Jose ; Hoesch, Lienhard ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1918-1929

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The portions of the N3H3 singlet potential energy surface corresponding to triaziridines (1), azimines (2) and triazenes (3) have been calculated by ab initio SCF using 3-21G, 6-31G, and 6-31G** basis sets. Minima and transition states were located by force gradient geometry optimization. The most important computation results are: (1) Triaziridines (1): The configuration at the 3 N-atoms is pyramidal. There are 2 stereoisomers, 1a and 1b. The c,t-isomer 1a has less energy than the c,c-isomer 1b. The 2 stereoisomerizations by N-inversion hve rather high activation energies. The N,N bonds in 1 are longer and weaker (STO-3G estimation) than in hydrazine. The N-homocycle 1 exhibits less ring strain than the C-homocycle cyclopropane or three-membered heterocycles. (2) Azimine (2): All 6 Atoms are in the same plane. There are 3 stereoisomers, 2a, 2b, and 2c. The order of ground state energies is (Z,Z) 〈 (E,Z) ≫ (E,E). The 2 N,N bond lengths correspond to multiplicity 1½. The electronic structure of 2 corresponds to a 1,3-dipole with almost equal delocalization of the 4 π-electrons over all 3 N-atoms. The negative net charge at the central N-atom is much less than that at the terminal N-atoms. Azimines should behave as π-donors in complexation with transition metals (3) Triazene (3): All 6 atoms are in the same plane. There are 2 stereoisomers, 3a and 3b. The order of ground-state energies is (E) 〈 (Z). The stereoisomerization proceeds as pure N-inversion. N-Inversion has a high energy barrier inversion at N(1) is faster than at N(2). One of the N,N bond lengths is typical for a double, the other for a single bond. The electronic structure of triazene 3 entails rather localized π- and p-electron pairs at N(1),N(2) and at N(3). Triazenes should behave as p-donors in complexation with transition metals. (4) -N3H3-Isomers: The order of ground-state energies is 3 〈 2 〈 1. The energy differences between these constitutional isomers are much larger than between the stereoisomers of each. The [1,2]-H shifts for conversions of 2 to 3 and the [1,3]-H shift for tautomerization of 3 have relatively high activation energies; both shifts can be excluded as modes of thermal, unimolecular transformations.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670730

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The Reaction of 4-Hydroperoxy-2,4,6-trimethylcyclohexa-2,5-dienone with Acetaldehyde. Formatino of the Bis(peroxyacetal) (1984)

Jefford, Charles W. ; Bernardinelli, Gérald ; McGoran, Ernest C.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1952-1956

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The reaction of 4-hydroperoxy-2,4,6-trimethylcyclohexa-2,5-dienone with acetaldehyde using trimethylsilyl trifluoromethanesulfonate as catalyst gives 1,1′-bis[(1,3,5-trimethyl-4-oxo-2,5-cyclohexadienyl) peroxy]diethyl ether (7) in 70% yield. The structure of this unusual acetal was determined by X-ray analysis.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670733

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The chemistry of drugs part IVPart III, see [1]., Configurations of antimalarials derived from qinghaosu: Dihydroqingyhaosu, artemether, and artesunic acid (1984)

Luo, Xuan-De ; Yeh, Herman J. C. ; Brossi, Arnold ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1515-1522

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The structures of the antimalarials dihydroqinghaosu (2), artemether (3), and artesunic acid (7a) derived from qinghaosu were elaborated by 1H-NMR spectroscopy, and supported with X-ray data obtained for 2 and 3. Several new derivatives, useful for the chemical characterization of dihydroqinghaosu (2) and artesunic acid (7a), were prepared.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670615

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Deoxy-nitrosugars, 7th communication6th Communication: [1]. Synthesis of methyl shikimate and of diethyl phosphashikimate from D-ribose (1984)

Mirza, Sohail ; Vasella, Andrea

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1562-1567

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The chain elongation of the deoxy-nitroribose 6 by a Michael addition to the vinyl-phosphonate 7 followed by a solvolysis gave the heptulosephosphonate 11 (87%). From 11, the key intermediates 15 and 16 (77%) were obtained by a highly diastereoselective reduction, followed by detritylation, periodate cleavage, and silylation. Methoxycarbonylation of 15 and 16 gave 17 and 18 which were converted into methyl shikimate (21; 79%) by intramolecular olefination and partial deprotection. Similarly, phosphonoylation of 16 gave 22 (99%) which was transformed into the diethyl phosphashikimate 2 (53% from 6).

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670621

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Mitteilungen - Communications (1984)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 2029-2030

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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.19840670743

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Errata (1984)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 2028-2028

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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.19840670742

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Masthead (1984)

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984)

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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.19840670801

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On the Nature of the 7-Norbornadienyllithiums. Preliminary Communication (1984)

Goldstein, Melvin J. ; Wenzel, Timothy T.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 2029-2036

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Lithium reductions of 7-chloronorbornadiene and of bis(7-norbornadienyl)mercury both provide (C7H7)2Li2 (5a). This product is accompanied by C7H7Li2Cl (5c) in the first case, and by C7H7Li (5b) in the second. The theoretically anticipated properties of all three organolithiums are apparent in the consistent Cs symmetry of their hydrocarbon ligands, their protolytic destruction by 12-crown-4, and their significant J(C(7), Li) (5a, 7.6; 5b, 16.0; 5c 8.9 Hz).

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670802

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Novel Variant of the Tricyclooctanone Approach to Cyclopentanoid Natural Products. Synthesis of (±)-Coriolin. Preliminary Communication (1984)

Demuth, Martin ; Ritterskamp, Peter ; Schaffner, Kurt

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 2023-2027

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: A total synthesis of the antitumor sesquiterpene coriolin (9; racemic) in 11 steps from 3,3,6-trimethylbicyclo[2.2.2]oct-7-ene-2,5-dione (2a/2b) is described (yield 2a/2b→8: 28%). The sequence is unprecedentedly short and avoids difficult separation problems. The key step in the scheme is a novel facet of oxadi-π-methane photochemistry, i.e., the steering by subtle steric effects of the β,γ-unsaturated ∊-diketone to undergo a regioselective photorearrangement involving one β,γ-enone partial chromophore. Furthermore, the overall phototransformation, which can be carried out at unusually high concentrations (≥20% solutions), involves also a Norrish type I process equilibrating the two epimeric starting enediones 2a and 2b in favour of the desired stereoisomer.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670741

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Synthese von optisch aktiven Carotinoiden mit 3,5,6-Trihydroxy-5-6-dihydro-β-Endgruppen (1984)

Buchecker, Richard ; Marti, Urs ; Eugster, Conrad Hans

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 2043-2056

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Syntheses of Optically Active Carotenoids with 3,5,6-Trihydroxy-5,6-dihydro β-End GroupsFor the specification of the relative and absolute configuration in carotenoids with 3,5,6-trihydroxy-5-6-dihydro β-end groups, several ionone derivatives and carotenoids bearing this end group were synthesized. Acid-catalyzed hydrolysis of (3S,5S,6R)- acetoxy-5,6-epoxy-5,6-dihydro-β-ionone (7) and of its (3S,5R,6S)-isomer (13) gave the diols 8 and 15, respectively, with exclusive inversion at c(5) (Scheme 2). Compared to this, mild acid hydrolysis of caroten-5-6-expoxides in the presence of H2O resulted in the formation of 5,6-diols with either inversion or retention of the configuration at C(6) (Scheme 3). Spectroscopic data allowed us to distinguish the relative configurations (3R*,5S*,6S*) (see A), (3R*,5R*,6R*) (see B), (3R*,5S*,6R*) (see C), and (3R*,5R*,6S*) (see D), of the 3,5,6-trihydroxy-5-6-dihydro β-end groups. Syntheses of the optically active carotene-hexols 20 and 21 and comparison with published data led to a revision of the structure of mectrazanthin (now formulated as 20), heteroxanthin (now formulated as 28), and further carotenoids with 3,5,6-trihydroxy end groups.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670804

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The Photoisomerization of 1,2,3,4,5-Pentamethyl-5-vinyl-1,3-cyclopentadiene (1984)

Burger, Ulrich ; Etienne, Robert

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 2057-2062

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The title compound 1 is shown to give, both upon direct irradiation at 254 nm and upon acetophenone-sensitized photolysis at 300 nm, the syn-vinyl-pentamethylhousene 5, which spontaneously rearranges in a [3,3]0sigmatropic process to give the bicyclo[3.2.0]heptadiene skeleton 2. Based on the photochemical behaviour of selectively deuterated starting material, the suggestion is made that the direct photolysis produces the vinylhousene skeleton by a classic electrocyclization, whereas the sensitized reaction reaches the same target via a di-π-methane rearrangement. The bicyclo[3.2.0]heptadiene derivative 2 give pentamethylhomoprismane 3 upon prolonged irradiation at 254 nm.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670805

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Conversion of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (mptp) and its 5-methyl analog into pyridinium saltsDedicated to Prof. Dr. H.C. Beyerman of the Laboratory of Organic Chemistry at the Technical Highschool in Delft, the Netherlands, on the occasion of his 65th birthday. (1984)

Gessner, Wieslaw ; Brossi, Arnold ; Shen, Rong-Sen ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 2037-2042

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Monoamine oxidase B metabolizes 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP; 1) first to 1-methyl-4-phenyl-2,3-dihydropyridinium salt (MPDP+; 5), and then to 1-methyl-4-phenylphridinium salt (MPP+; 7). Chemical synthesis of MPDP+ and its 5-methyl analog 6 was accomplished from the N-oxides 3 and 4 of MPTP and its 5-methyl analog, respectively, by a Polonovski reaction. Oxidation of MPDP+ to MPPM+ was accomplished with air, and greatly accelerated by Pt catalyst. Reduction of MPDP+ and MPP+ with NaBH4 afforded MPTP.

Zusätzliches Material: 2 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670803

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Photochemical reactions. 140th Communication139th Communication, see [1]. Acid-catalyzed rearrangement and electron transfer photooxygenation of cyclopropanols and their silyl ethers (1984)

Scheller, Markus E. ; Mathies, Peter ; Petter, Walter ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1748-1754

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: On acid-catalyzed hydrolysis, the tricyclic compounds 2 and 10, incorporating cyclopropyl-silyl-ether moieties undergo rearrangement to the cis-decalones 3 and 7, respectively. Hydrolysis of 2 and 10 in the presence of oxygen leads additionally to the formation of the 1,2-dioxolan-3-ols 9 and 13, respectively, which involves an electron-transfer oxygenation process as could be demonstrated by photooxygenation of the silyl ether 10 and the cyclopropanol 14 in the presence of 9,10-dicyanoanthracene. The configurations of 3 and 9 were assigned by X-ray analysis of the latter compound as well as of the p-nitrobenzoate 8 of 3.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670712

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Experiments on the total synthesis of Lysolipin I. Part IIPart I: [1]. Michael addition of 1,3-cyclohexanedione to quinone acetalsThese results are part of the planned Ph.D. thesis of U. W. (1984)

Duthaler, Rudolf O. ; Wegmann, Urs H.-U.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 1755-1766

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Base-catalyzed reaction of 1,3-cyclohexanedione (3) with the quinone monoacetals 4 and 7 leads to the polycyclic products 5 and 8, respectively, and in the case of 4 to variable amounts of dibenzofuranone 6. The 2-arylcyclohexanedione 9, on the other hand, is isolated from the reaction of 3 and bisacetal 11 catalyzed by ZnCl2 (Scheme 2). Treatment of the adduct 8 with (CH3O)2SO2/K2CO3 results in cleavage of teh heterocyclic ring by a retro-Michael reaction affording teh liable enone 23 which was further transformed to 24 by selective hydrogenation. The 8-acetoxydibenzofuranone 22 is obtainable from 8 by acid treatment and acetylation (Scheme 4). The reactions of the silylenol ethers 27 and 35 with quinone monoacetals were very complex (Scheme 6). The desired arylcyclohexanone derivatives 28 and 36 were formed in very low yields. Under certain conditions (elevated temperature or strong Lewis acids as catalysts), single-electron transfer or addition to the ene-acetal rather than to the enone function of the quinone monoacetals became predominant. In connection with this study, the sensitive 2-methoxy-p-benzoquinone monoacetals 15 (Scheme 3) and 29 (Scheme 6) have been prepared and characterized.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670713

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The Synthesis and Structure of Pentacarbonyl (5H-dipyrrolo[1,2-c: 2′,1′-e]imidazol-5-yl)manganese (1984)

Burger, Ulrich ; Perret, Celia ; Bernardinelli, Gérald ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 2063-2067

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The dipyrroloimidazolyl ligand is found to bind the pentacarbonylmanganese group to its central ring via a carbon-metal σ-bond. This bonding mode differs greatly from that of known imidazole complexes and from the pentahapto mode encountered with the isoelectronic fluorenyl ligand. The X-ray structure of the title compound is reported.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670806

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Substitution électrophile aromatique dans l'anhydride sulfureux liquide. Influence de la concentration en bromure et rôle du solvant sur la réactivité des anisoles au cours de la réaction de bromation (1984)

Castellonése, Paul ; Villa, Pierre

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 2087-2099

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Electrophilic Aromatic Substitution in Liquid Sulfur Dioxide. Kinetic Dependance of Rate on the Bromide Concentration and Influence of the Solvent during the Course of the ReactionOn the reported data for bromination of anisole and eleven of its derivatives in liquid SO2, it was shown that, with a large excess of bromide, the rate of reaction, obeys a first-order law. Rate constants thus obtained do not discriminate between the two different forms of bromide, e.g. Br2 and Br-3 present as the A+Br-3 form, and corrections were made by use of the apparent equilibrium constant K′ for tribromide formation. The variations of rate constants with initial concentration of bromide has been studied and the effect results in a retardation of the bromination rate. Moreover, the ratio [Br2] [A+Br-]T, which is constant during an experiment, varies with initial bromide concentrations, this variation affecting the total rate. To account for the bromide effect on the reactivity, variations of ko,pg {1 + K′[A+Br-]T}VS[A+Br-]T were studied over a 0.01 to 1M range of bromide concentration. The mechanism proposed shows that liquid SO2 helps the reactive intermediate to be deprotonated and because of solvation of reactive species this step would probably be rate determining. Bromination by molecular bromine is more sensitive to substituent effects in liquid SO2 than in water. This result is ascribed to the +M effect of the methoxy group which increase the conjugation of ortho-substituted derivatives (p+p = -7.83; p+o= -10.47).

Zusätzliches Material: 5 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670810

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An Improved Liquid-Phase Synthesis of Simple AlkylpyridinesParts of this work have already appeared in preliminary form [1]. (1984)

Grayson, J. Ian ; Dinkel, Rolf

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 2100-2110

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The synthesis of pyridines from mixtures of aldehydes or ketones NH3 in the liquid phase has been reinvestigated, using continuous dosage of the carbonyl components to the reaction mixture. The main product from the reaction of acetaldehyde and formaldehyde is 3-methylpyridine (6), which is also the main product from the reaction of acrolein or a mixture of crotonaldehyde and formaldehyde under the same conditions. The reaction of other aldehydes with formaldehyde give 3,5-dialklypyridines, e.g. 10, 16. Acetone reacts with either formaldehyde or acetaldehyde to give polysubstituted alkylpyridines. A mechanistic pathway is proposed which accounts for the formation of the observed products.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670811

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Hyperbolic Reaction Curves with Concentration-Independent Relaxation Times (1984)

Balakrishnan, Karappulli P. ; Gampp, Harald ; Zuberbühler, Andreas D.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 2155-2160

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Hyperbolic reaction curves with concentration-independent relaxation times are obtained from the simple reaction scheme A⇌I + P; A + I → P. While a mathematically perfect hyperbola is only obtained, if two of the three rate constants are accidentally degenerate, the same function can still be used as a very close approximation in the general case, and the differences may go unnoticed even for well-defined stopped-flow experiments. In view of the simplicity of the reaction, it is suggested that reaction curves with second-order (hyperbolic) shapes, but concentration-independent relaxation times may be a common feature in chemical kinetics.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670815

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Nukleophile Reaktionen an 2-Phenylindolenin-3-onen (1984)

Adam, Jean-Marie ; Winkler, Tammo

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 2186-2191

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Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Nucleophilic Reactions on 2-Phenylindolenin-3-onesNucleophilic reagents such as 4-nitrophenylhydrazine, malonic acid derivatives, and hydrogen peroxide react with 2-phenylindolenin-3-ones giving, in the first step, addition products to the (d) N=C(2) bond. This addition can be reversible, but in most cases new rearrangement products are formed. The structure of the new compounds were elucidated by 1H- and 13C-NMR spectroscopy.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670820

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93

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Stabilities and Structures of Cu(II) Complexes with Linear Pentadentate Ligands by EPR Spectroscopy (1984)

Gampp, Harald

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 2164-2174

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The pH-dependent equilibria between Cu(II) and the potentially pentadentate ligands 4,7,10-triazatridecane-1,13-diamine (1) and 1,9bis(2-hydroxyphenyl)-2,5,8-triazanonane (2) have been studied in aq. solution at 298 K by EPR titration. Each ligand forms complexes CuLHx (x=1,2,3) with strongly overlapping spectra. By using a recently developed algorithm, which does not need nay information with regard to the spectra of the species, stability constants and spectra were calculated from the EPR titration data. The anisotropic EPR spectra of the complexes were measured at 153 K and display axial or nearly axial symmetry (g∥ 〉 g⊥) in each case. Based on the spectral parameters the assignment of the structures of the complexes was possible. With 1 and 2 the protonated complexes are equatorially coordinated, whereas in the fully deprotonated complexes an additional axial interaction occurs which is stronger with 2 than with 1.The results of this study show that EPR spectroscopy is a useful method for investigating equilibrium systems of Cu2+ even in complicated cases where minor species occur and where the individual spectra are unknown and strongly overlapping.

Zusätzliches Material: 5 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670817

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94

Digitale Medien

Synthese eines 2,5,7,10-substituierten 1,6-Methano[10]annulens, seine Methylierung, Ätherspaltung und DeprotonierungHerrn Kollegen Gerhard Fritz, Karlsruhe, mit allen guten Wünschen zum 65. Geburtstag gewidmet - in dankbarer Erinnerung and die gemeinsamen Jahre in der Fakultät Chemie der Universität Karlsruhe (TH) (1984)

Neidlen, Richard ; Hartz, Georg

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 2192-2197

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Synthesis of a 2,5,7,10-Substituted 1,6-Methanol[10]annulene, its Methylation, Ether Cleavage; and DeprotonationThe synthesis of 2,7 -di(tert -butoxy)-1,6-methanol[10]annulene derivatives 2 and 3 are described. Methylation of 3 gave 4, and 4 was transformed, on treatment with p-toluene sulfonic acid, to the salt 5. Basic reagents deprotonated 5; the resulting solution was analyzed by 1H-NMR spectroscopy.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670821

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95

Digitale Medien

Synthesis and Crystal Structure of a Peroxo-Bridged Binuclear Rhodium (III) Complex and its Superoxo-Bridged Analogue (1984)

Springborg, John ; Zehnder, Margareta

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 2218-2225

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The reaction of the ammonia diol [(NH3)4Rh(OH)2Rh(NH3)4]4+with H2O2 Yields among other products a peroxo-bridged dimeric species [(NH3)4Rh(O2)(OH)Rh(NH3)3(H2O)](CIO4)3. Its structure was determined by single-crystal X-ray diffraction. The crystals are monoclinic with space group P21/n and lattice constants a=12.269 (5) Å, b=10.769(4) Å, c=15.964(4) Å, β=107.17(3)°. The dihedral angle of the RhOORh group in the bimetallic ring deviates by 62δ from planarity. The peroxo-bridged complex was found to disproportionate in 1M HCIO4 and a red superoxo-bridged complex. [(NH3)4Rh(O2)(OH)Rh(NH3)3(H2O)](NO3)4, was isolated. Its structure was solved by single-crystal X-ray diffraction. The crystals are orthorhombic with space group Pna 2, and lattice constants a=14.997(5) Å, b=11.952(4) Å, C=10.489(4) Å. The dihedral angle off the RhOORh group deviates by 7δ from planarity.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670825

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96

Digitale Medien

Planarisation of Tetracoordinate Carbon Atom. A Further Route ot (all-cis)-[5.5.5.5]Fenestrane (1984)

Luyten, Marcel ; Keese, Reinhart

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 2242-2245

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The synthesis of (all-cis)-[5.5.5.5]fenestrane (3) from dicyclopentadiene is reported. Key step is the Pd-catalyzed reductive deoxygenation of an appropriately substituted cyclooctanone, which leads to transannular C,C-bond formation.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670829

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97

Digitale Medien

Gerüstumlagerung eines α,β -ungesättigten γ,δ-Epoxiketons bei der Birch-Reduktion: Strukturaufklärung mittels 13C-INADEQUATE-NMR-Spektroskopie (1984)

Kreiser, Wolfgang ; Rüschenbaum, Voker ; Bauer, Hans ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 2231-2235

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Skeleton Rearrangement of an α-β-Unsaturated γ,δ-Epoxyketone during Birch Reduction: Structure Elucidation by Means of 13C-INADEQUATE-NMR SpectroscopyWhen the γ-epoxide 2 of β-ionone is treated under standard Birch-reduction conditions, unexpectedly a 70% combined yield of regioisomeric octalones 4 and 5 is isolated. These products unquestionably result form cleavage of the central epoxide C=C bond. The structure of compounds 4 and 5 could be determined by means of 13C-INADEQUATE-NMR spectroscopy.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670827

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98

Digitale Medien

Biogenetic-Type Total Synthesis of (±)-2-Deoxystemodinone. Preliminary Communication (1984)

Lupi, Alessandro ; Patamia, Maria ; Grgurina, Ingeborg ; [weitere]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 2261-2263

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: A biogenetic-type total synthesis of(±)-2-deoxystemodinone (1), by solvolytic rearrangement of the 1-methyl[2.2.2]oct-2-yl methanesulphonate 4, is described.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670832

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99

Digitale Medien

Conformational Equilibria in trans-1,2-Diarylethylenes Manifested in their Emission in Solution. Part VI. Heterocyclic Analogues, their Triplets and ExciplexesDedicated to Prof. A. E. Siegrist, Basel (1984)

Wismontski-Knittel, T. ; Das, P. K. ; Fischer, E.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 2246-2253

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Solutions of heterocyclic analogues of 2-styrylnaphthalene (2-St-N), with benzo[b]thiophene and benzo[b]furan groups replacing the 2-naphthyl group, exhibit emission anomalies similar to those reported for 2-St-N, the most prominent one being a variation of the emission spectra with the excitation wavelength. The exciplexes formed when emission is quenched by N,N-dimethylaniline (DMA) show a smaller variation of their emission maxima. Ground-state rotamers may be responsible for the anomalies. The lifetimes of regular fluorescence in toluene are ≤ 2 ns, and our equipment did not allow to determine whether or not the decay is mono-exponential. Exciplex lifetimes in toluene are 20-30 ns. The triplets (λmaxT = 500-520 nm) are characterized by short lifetimes (180-190 ns) and appear to have substantial contributions from twisted configurations.

Zusätzliches Material: 5 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670830

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100

Digitale Medien

Metal complexes with macrocyclic ligands. Part XIXPart XVIII: [1].. Synthesis and Cu2+-complexes of a series of 12-, 14- and 16-membered cis- and trans-N2S2-macrocycles (1984)

Siegfried, Liselotte ; Kaden, Thomas A.

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 67 (1984), S. 29-38

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ISSN: 0018-019X

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: A series of 12-, 14-, and 16-membered N2S2-macrocycles (9-11 and 19-21) with cis and trans-arrangement of the heteroatoms have been synthesized by high-dilution cyclization and subsequent reduction of the amides with B2H6. With these ligands the corresponding Cu2+-complexes were prepared and their UV/VIS spectra, their electrochemistry and their EPR properties have been studied. Generally three absorption bands at 270-320 nm, 330-370 nm and 530-620 nm can be observed in aqueous solution and these have been assigned to the N→Cu2+ and S→Cu2+ charge-transfer bands and to the d-d* transition, respectively. The cyclic voltammetry in CH3CN shows in all cases a reversible or quasi-reversible Cu2+/Cu+-transition at potentials of 10-480 mV against SHE. The values of g‖ and A‖ obtained from EPR spectra indicate that the geometry of the Cu2+-complex of the 14-membered cis-N2S2-macrocycle is less distorted than that of the other complexes.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/hlca.19840670105

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