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  • 1
    Electronic Resource
    Electronic Resource
    Synthesis of benzopyran derivatives, XV Preparation of arylsulfonyloxy-2,2-dimethyl-2H-chromenes (1990)
    Springer
    Monatshefte für Chemie 121 (1990), S. 403-411 
    Details
    ISSN: 1434-4475
    Keywords: 2,2-Dimethyl-4-chromanones ; Reduction with NaBH4 ; 2,2-Dimethyl-4-hydroxychromans ; Dehydration ; Conformational analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Reduktion von Arylsulfonyloxy-2,2-dimethyl-4-chromanonen (6–15) und anschließende Dehydratisierung liefert Arylsulfonyloxy-2,2-dimethyl-2H-chromene (26–35).
    Notes: Summary Arylsulfonyloxy-2,2-dimethyl-2H-chromenes (26–35) have been synthesized by reduction of arylsulfonyloxy-2,2-dimethyl-4-chromanones (6–15) followed by dehydration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00809457
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  • 2
    Electronic Resource
    Electronic Resource
    Electron-impact induced fragmentation of spiro-1-pyrazolines (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 626-630 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The positive-ion electron impact mass spectra of twelve spiro-1-pyrazolines have been recorded as 70 eV electron energy and the dat analyzed to elucidate their fragmentation pathways. None of these compounds gave abundant molecular ions (M+) due to the instability of the pyrazoline ring. The first step in the decomposition of M+ ions is the elimination of a nitrogen molecule followed by a rearrangement resulting in the formation of the cation radical [M-28]+, the decomposition of which is discussed in detail. The proposed fragmentation pathways and their mechanisms are supported by high-resolution data, linked-scan measurements at constant B/E and collision-induced dissociation-mass-analyzed ion kinetic energy spectra.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290061008
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  • 3
    Electronic Resource
    Electronic Resource
    An Efficient Procedure for the Preparation of 3-Acetyl-2,3-dihydrobenzo-thiazoles by Ring Contraction of 2,4-Diaryl-2,3-dihydro-1,5-benzothiazepines under Acetylating ConditionsThis paper is considered as Part 33 of A. Lévai's series: Oxazepines and Thiazepines. Part 32: A. Lévai, Sci. Pharm. 1996, 64, 523-530. (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 995-998 
    Details
    ISSN: 0947-3440
    Keywords: Acetylation ; Benzothiazoles ; NMR spectroscopy ; Ring contractions ; Structure elucidation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of 2,4-diaryl-2,3-dihydro-1,5-benzothiazepines 1 with a mixture of acetic anhydride and pyridine afforded 3-acetyl-2,3-dihydrobenzothiazoles 2 as sole products in good yields. Stereochemistry and the hindered rotation of the amide group were studied by means of NMR spectroscopy and the results were corroborated by AM1 calculations. A reaction mechanism for the ring contraction is proposed.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970530
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  • 4
    Electronic Resource
    Electronic Resource
    Isomerization and conjugation characteristics of the C=N double bond. IIIFor Part II see Ref. 1. - 15N NMR studies of tautomerism in 2-phenylamino-2-thiazoline and its thiazine analogue (1982)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 19 (1982), S. 219-221 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 15N NMR Spectroscopy shows, contrary to earlier suggestions, that 2-phenylamino-2-thiazoline and its thiazine analogue are present in chloroform as an equilibrium of imino and amino tautomers in the ratio of 62:38 and 74:26, respectively.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270190412
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  • 5
    Electronic Resource
    Electronic Resource
    Single-electron Transfer-initiated Thermal Reactions of Arylmethyl Halides, IX. The Reaction of 2-Bromo-N,N-dimethyl-2,2-diphenylacetamide with Triethylamine in Benzene (1985)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 118 (1985), S. 1273-1277 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Durch Ein-Elektronen-Übergang ausgelöste thermische Reaktionen von Arylmethylhalogeniden, IX. Die Reaktion von 2-Brom-N,N-dimethyl-2,2-diphenylacetamid mit Triethylamin in BenzolDas Halogenamid 1a liefert mit Triethylamin in siedendem Benzol 41 - 48% des Dimeren 3 als Hauptprodukt. Andererseits führt die Thermolyse von 1f in Benzol in Gegenwart von Triethylamin zu 1c und 8a. Die Bildung von 3 erfolgt über die Radikale 4, die ihrerseits das Produkt einer Ein-Elektronen-Übergangs-Reaktion mit Triethylamin als Elektron-Donor [Gl. (1)] sind. Der Übergang der Radikale 4 in das Dimere 3 verläuft entsprechend der Reaktionsfolge (2) + (4) + (5) (carbanionischer Mechanismus der Dimeren-Bildung).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19851180342
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  • 6
    Electronic Resource
    Electronic Resource
    as-Triazine und kondensierte Derivate, XVIII. Zur Ring-Ketten-Tautomerie bei 3-Hydroxythiazolo[3,2-b]-as-triazin-7-onen (1977)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 110 (1977), S. 1492-1496 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: as-Triazines and Condensed Derivatives, XVIII. Ring-Chain Tautomerism in 3-Hydroxythiazolo[3,2-b]-as-triazin-7-onesThe hydroxyl groups of the most stable conformer (y) of 3-hydroxythiazolo[3,2-b]-as-triazin-7-one (2a) as well as of the related compound 4 are axial.  -  At elevated temperatures, the AB signal of the CH2 group in the 1H-NMR spectrum of compound 2b collapses, as a result of tautomerization to 3b, into a singlet. ΔG≠ is 17.0 kcal/mole at the coalescence temperature (68°C). In agreement with the decreasing order of the +I effect in the series CH3 〉 CH2Cl 〉 H, no similar tautomerizations take place up to 130°C in the case of compounds 2a and 2c. Compound 4, however, exists at elevated temperatures as an equilibrium mixture with the corresponding “open-chain” form 5.  -  The singlet of the CH2Cl group of compound 2c is transformed, at elevated temperatures, into an AB quadruplet. An explanation for this apparent anomaly is suggested.
    Notes: Das stabilste Konformere (y) des 3-Hydroxythiazolo[3,2-b]-as-triazin-7-ons (2a) enthält eine axiale OH-Gruppe, ebenso wie das der verwandten Verbindung 4.  -  Bei Erhöhung der Temperatur fällt das AB-Signal der CH2-Gruppe im 1H-NMR-Spektrum von 2b als Folge der Tautomerisierung zu 3b in ein Singulett zusammen. Der ΔG≠-Wert bei der Koaleszenztemperatur (68°C) beträgt 17.0 kcal/mol. Im Einklang mit der Abnahme des +I-Effektes in der Reihenfolge CH3 〉 CH2Cl 〉 H erfolgt bei den Verbindungen 2a und 2c bis 130°C keine ähnliche Tautomerisierung. Die Verbindung 4 liegt jedoch bei erhöhter Temperatur im Gleichgewicht mit der „offenkettigen“ Form 5 vor.  -  Bei steigender Temperatur wandelt sich das Singulett der CH2Cl-Gruppe von 2c in ein Quadruplett um. Eine Erklärung für diese scheinbare Anomalie wird gegeben.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19771100432
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  • 7
    Electronic Resource
    Electronic Resource
    Alkaloide mit Indolo[2′,3′:3,4]pyrido [2,1-b]chinazolin-Struktur, VII. Synthese und Untersuchungen des cis-und trans-Hexahydrorutaecarpins (1977)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1977 (1977), S. 529-536 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Alkaloids with Indolo[2′,3′:3,4]pyrido[2,1-b]quinazoline Structure, VII.  -  Synthesis and Structure of cis-and trans-HexahydrorutecarpineIn a study on cis- and trans-hexahydrorutecarpine (4 and 5, resp.) it was established that the C-ring in 5 is flexible, but nevertheless exists in a preferred conformation. This explains the anomalies observed in the 1H-NMR spectrum. A complete assignment of the 13C-NMR signals of 4 and 5, as well as of rutecarpine (6) and debenzorutecarpine (7) is given.
    Notes: Bei der Untersuchung von cis- und trans-Hexahydrorutaecarpin (4 bzw. 5) wurde festgestellt, daß der C-Ring in 5 zwar flexibel ist, jedoch in einer bevorzugten Konformation vorliegt. Dies erklärt die im 1 H-NMR-Spektrum beobachteten Anomalien. Eine vollständige Zuordnung der 13C-NMR-Signale von 4 und 5, sowie von Rutaecarpin (6) und dem Desbenzorutaecarpin (7) wird angegeben.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.197719770402
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  • 8
    Electronic Resource
    Electronic Resource
    N-4-Epimere von quaternären Yohimbin-Derivaten (1978)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1978 (1978), S. 1096-1102 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: N-4-Epimers of Quaternary Yohimbine DerivativesYohimbine (1), β-yohimbine (2), and yohimbinone (3), on quaternization at N-4 with methyl iodide, give α- and β-diastereoisomers, resp., in a ratio of 3:2. The configuration at N-4 has been determined by circular dichroism (CD). The cotton effects within the transitions 1Lb, 1Bb, and 1Ba of the indole chromophore are mainly determined by the chirality of the second sphere, for the CD within the 1La-band contributions from the third sphere are, however, stronger. From CD it follows also that yohimbinium chloride (5) in solution is present as a mixture of N-4-diastereoisomers.
    Notes: Yohimbin (1), β-Yohimbin (2) und Yohimbinon (3) liefern bei der Quaternierung an N-4 mit Methyliodid jeweils α- und β-Diastereoisomere im Verhältnis 3:2. Die Konfiguration an N-4 wurde durch Circulardichroismus (CD) bestimmt. Die Cotton-Effekte innerhalb der Übergänge 1Lb, 1Bb und 1Ba des Indolchromophors werden hierbei wesentlich durch die Chiralität der zweiten Sphäre determiniert; beim CD innerhalb der 1La-Bande sind Beiträge der dritten Sphäre dagegen stärker. Aus dem CD folgt, daβ das Yohimbiniumchlorid (5) in Lösung als N-4-Diastereomerengemisch vorliegt.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.197819780707
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  • 9
    Electronic Resource
    Electronic Resource
    Stereochemische Untersuchung der 4-Benzyliden-1,2,3,4-tetrahydro-3-isochinolinone und ihrer hydrierten Derivate (1978)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1978 (1978), S. 1103-1110 
    Details
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Stereochemical Studies on 4-Benzylidene-1,2,3,4-tetrahydro-3-isoquinolinones and their Hydrogenated DerivativesThe structures of 4-benzylidene-1-phenyl-1,2,3,4-tetrahydro-3-isoquinolinone 1E, its photoisomer 1Z, and of the products 3a, b obtained by catalytic hydrogenation were determined using 1H-, LIS-1H-, 13C-NMR, and NOE measurements. The catalytic hydrogenation of the benzylidene derivatives 1E and 1Z was proven to be stereoselective.
    Notes: Die Strukturen von 4-Benzyliden-1-phenyl-1,2,3,4-tetrahydro-3-isochinolinon 1E, seinem Photoisomeren 1Z sowie der durch katalytische Hydrierung gewonnenen Verbindungen 3a und 3b wurden mittels 1H-, LIS-1H-, 13C-NMR- und NOE-Messungen bestimmt. Es zeigte sich, daβ die katalytische Hydrierung der Benzylidenderivate 1E und 1Z stereoselektiv verläuft.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.197819780708
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  • 10
    Electronic Resource
    Electronic Resource
    1,3-Dipolare Cycloadditionen von Azomethin-yliden (1982)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1982 (1982), S. 2146-2152 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,3-Dipolar Cycloadditions of Azomethine Ylides1,3-Dipolar cycloadditions of the azomethine ylides 2 and 9 with Schiff′s bases have been investigated. Depending on the structures of both the dipolarophiles and the dipoles, cycloadducts of “exo” and/or “endo” type were formed.
    Notes: Die 1,3-dipolaren Cycloadditionen der Azomethin-ylide 2 und 9 mit Schiffschen Basen wurden untersucht. Es bilden sich Cycloaddukte vom “exo”-und/oder “endo”-Typ in Abhängigkeit von der Struktur des Dipolarophils und des Dipols.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198219821205
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