Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Short Syntheses of (±)-Grandisol and (±) Lineatin via, a common Intermediate (1987)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 1302-1306 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A 6-step synthesis of (±)-grandisol (1) is presented, which involves dichloroketene addition to 3-methyl-3-butenyl acetate (4), reductive dechlorination of the adduct 6 to the ketone 7 and saponification to 8, aldolization of 7 or 8 with acetone and cyclization to the bicyclic ketone 9, Wolff-kishner, reduction to 14, and finally ring opening to 1. Since 9 is a known intermediate of the synthesis of (±)-lineatin (2), the latter can now be obtained in 6 steps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19870700510
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Synthese von enantiomerenreinen Violaxanthinen und verwandten Verbindungen (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 931-956 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses of Enantiomerically Pure Violaxanthins and Related CompoundsThe epoxides 16 and ent-16, prepared by Sharpless-Katsuki oxidation of 15 in excellent yield and very high enantiomeric purity, were used as synthons for the preparation of (+)-(S)-didehydrovomifoliol (45), (+)-(6S, 7E, 9E)-abscisic ester 46, (+)-(6S, 7E, 9Z)-abscsic ester 47, (-)-(3S, 7E, 9E)-xanthoxin (49), (-)-(3R, 7E, 9E)-xanthoxin (50), (3S, 5R, 6S, 3′S,5′R, 6′S, all-E)-violaxanthin (1) (3R, 5R,6S,3′R,5′R,6′S, all-E)-violaxanthin (55) and their (9Z) (see 53, 57), (13Z) (see 54, 58), and (15Z) (see 60) isomers. The novel violadione (61) was prepared from 1 by oxidation with DMSO/Ac2O. By base treatment, 61 was converted into violadienedione (62), a potential precursor of carotenoids with phenolic end groups.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710502
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Cyclobut-2-enones from Alkynes via Dichlorocyclobut-2-enonesIn part taken from the Ph.D. thesis of A.A.A., University of Zürich, 1986. (1987)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 321-328 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The [2 + 2]-cycloaddition of dichloroketene (prepared in situ from CCl3COCl and Zn(Cu)) with three alkynes 1a-c to form 2,3-dimethyl-(2a), 2,3-diethyl-(2b) and 3-butyl-4,4-dichlorocyclobut-2-enone (2c) proceeds rapidly in the absence of POCl3. The primary products 2a-c rearrange in situ to the 2,4-dichlorocyclobut-2-enones 3a-c under the influence of ZnCL2 produced during the reaction. ZnCl2 converts both 2a and 3a into a 4:6 equilibrium mixture of the two; this isomerization does not occur with LiCl. The Cl-atoms of both 2a, b and 3a, band of 2c may reductively be removed with Zn(Cu) in AcOH/pyridine to afford the alkylcyclobutenones 4a-c. Without pyridine, this reduction gives ca. 1:1 mixtures of the double-bond isomers 4 and 5 in low yields. The cyclobutenones 2c and 4c may be deuterated by CD3COOD in the presence of pyridine. D-Atom is introduced into 2c at C(4) and at C(γ), and into 4c at C(2) and C(4). A mechanism for this deuteration is considered, which does not involve a cyclobutadienolate 7, but rather a cyclobutenolate of type 8. The reductions of 2 and 3 to 4 might also pass through the same type of intermediate 8.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19870700208
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Synthesis and Rearrangement of 7-Halobicyclo[3.2.0]hept-2-en-6-ols (1977)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 60 (1977), S. 1528-1544 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthese und Umlagerung von 7-Halo-bicyclo[3.2.0]hept-2-en-6-olenDie Reaktion von verschiedenen 7-halogen-substituierten Bicyclo[3.2.0]hept-2-en-6-onen mit komplexen Metallhydriden oder mit Methylmagnesiumiodid zu den entsprechenden 7-Halo-bicyclo[3.2.0]hept-2-en-6-olen verläuft unter Angriff des Nucleophils trans zum Halogen, um dem vicinalen Kohlenstoff-Halogen-Dipol auszuweichen. In Gegenwart von starken Basen unterliegen die Halohydrine einer Umlagerung, die je nach der durch die intramolekularen Wechselwirkungen bedingten Konformation, entweder unter Hydridverschiebung zu Bicyclo[3.2.0]hept-2-en-6-onen oder, unter Ringverengung, zu Bicyclo[3.1.0]hex-2-en-6-carbaldehyden führt.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19770600510
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Ein meta-Xylylen durch Bamford-Stevens-Reaktion eines Fulven-Keten-Addukts (1984)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 67 (1984), S. 1379-1385 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A meta-Xylylene by Bamford-Stevens Reaction of a Fulvene-Ketene-AdductHeating the sodium salt 8 of the tosylhydrazone 4 of 4-isopropyliden-7,7-dimethylbicyclo[3.2.0]hept-2-en-6-one (3; obtained by the addition of dimethylketene to 6,6-dimethylfulvene (1)), in diglyme at 130° led to the cotamethyl-[2.2]metacyclophane 10 (17%). The latter probably was formed by dimerization of the non-Kékulé molecule m-xylylene 14, which, in turn, could have arisen via the homofulvene 13 from the carbene 12. A second product in the thermolysis of 8 was the tricycle 9 (9 %), as a result of an intramolecular insertion of the carbene C-atom in 12 into a methyl C,H-bond. Further products were the azines 11a, 11b (50%), of the type known as byproducts in Bamford-Stevens reactions. Heating dry 8 afforded 9 (9%) and the two benzene derivatives 15 (9%) and 16 (3%). The tosylhydrazone 4 could be recovered by reaction of 11a, 11b with p-toluenesulfonohydrazide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19840670525
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Acid-Catalyzed Rearrangements of Vinylketene/Cyclopentadiene Adducts (1982)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 65 (1982), S. 1563-1575 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Säurekatalysierte Umlagerungen von Vinylketen/Cyciopentadien-AdduktenVier Alkyl-vinylketene (7b-e), in situ durch 1,4-Eleminierung von HCl aus den entsprechenden α,β-ungesättigten Acylchloriden hergestellt, wurden mit Cyclopen-tadien umgesetzt. Durch [2 + 2]-Cycloaddition entstanden 7-alkyl-7-vinylsubstituierte Bicyclo[3.2.0]hept-2-en-6-one 8/9. Das Stereoisomerenverhältnis 8:9 hängt von der relativen Grösse der Ketensubstituenten ab. Die Vinylketen/Cyclopen-tadien-Addukte 8/9 enthalten ein α-Vinylcyclobutanon-, ein Cope- und (bei 8f) ein Allylchlorid-System. Unter dem Einfluss von Säuren (meistens BF3-Ätherat) wurden bei 8/9 vier verschiedene Typen von Umlagerungsreaktionen beobachtet, nämlich, je nach dem Substitutionsmuster: [l,3]-Alkyl-Wanderungzu Bicyclo[4.3.0]-nonadienonen 12, [l,2]-Acyl-Wanderung zu Bicyclo[3.3.0]octenonen 13, [3,3]-Cope-Umlagerung zu Bicyclo[4.2.1]nonadienonen 14 oder [l,3]-Halogen-Wanderung zu 7-AlkylidenbicycIo[3.2.0]heptenonen 15. Die [l,3]-Alkyl- und [l,2]-Acyl-Wanderun-gen konkurrieren mit der Cope-Umlagerung, wobei auch die Konfiguration an C(7) der Vinylketen/Cyclopentadien-Addukte (8 bzw. 9) und das Lösungsmittel eine Rolle spielen können.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19820650530
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Addition of Vinylketenes to Enamines. A Method for the Preparation of 6,6-Dialkylcyclohexa-2,4-dienones and 4,4-Dialkyl-2-vinylcyclobutenones (1982)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 65 (1982), S. 2230-2241 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Addition von Vinylketenen an Enamine. Eine Methode zur Herstellung von 6,6-Dialkylcyclohexa-2,4-dienonenund4,4-Dialkyl-2-vinylcyelobutenonenDrei Enamine (1-3) wurden mit fünf Vinylketenen (5a-5e) (s. Schema 2) zur Reaktion gebracht. Die Vinylketene wurden in situ durch HCl-Eliminierung aus α,β-ungesättigten Säurechloriden mit Triäthylamin hergestellt. Die Cycloadditionen von 1-3 an 5a-5e führten zu 6,6-Dialkyl-5-dialkylaminoeyclohex-2-enonen (kurz: Cyclohexenone) bzw. zu 3-Dialkylamino-4,4-dimethyl-2-vinylcyclobutanonen (kurz: Vinylcyclobutanone) oder zu einem Gemisch der beiden, je nach Natur der Partner bzw. des Lösungsmittels (s. Tab. 1). Durch oxydative Amin-Eliminierung wurden die Cyclohexenone in 6,6-Dialkylcyclohexa-2,4-dienone und die Vinylcyclobutanone in 4,4-Dialkyl-2-vinylcyclobutenone übergefuhrt.Diese Reaktion stellt eine einfache Synthese von verschieden substituierten 6.6-Dialkylcyclohexa-2,4-dienonen bzw. 4,4-Dialkyl-2-vinylcyclobutenonen (siehe Schema 1) dar.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19820650728
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Reversible Umlagerung eines cis-2-Vinyl-cyclopropylformaldehydes zu einem Dihydrooxepin. Vorläufige Mitteilung (1965)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 48 (1965), S. 1985-1987 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Evidence is given for a fast reversible 2-vinylcyclopropylformaldehyde-dihydro-oxepine rearrangement. Bicyclo[3.1.0]hex-2-ene-6-endo-formaldehyde and 2-oxa-bicylo[3.2.1]octa-3,6-diene coexist in a 7:3 equilibrium, which is pulled in the direction of the enol ether by a cycloaddition with tetracyanoethylene, and in the direction of the aldehyde by interaction with LiAlH4, Ag2O or NaHSO3. Decomposition of the pure hydrogensulfite adduct of the aldehyde refurnishes the 7:3 mixture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19650480819
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Isomerisierungen und Umlagerungen in Bicyclischen Systemen via cyclopropan-carbaldehyd-enamine (1974)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 57 (1974), S. 734-748 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The pyrrolidino-aminal (4) of bicyclo[3.1.0]hex-2-ene-6-endo-carbaldehyde (3) underwent a facile (80°), mildly acid catalyzed isomerization to the corresponding exo-aminal (6), which was characterized by hydrolysis to bicyclo[3.1.0]hex-2-ene-6-exo-carbaldehyde (7).At higher temperatures (140°), the two aminals 4 and 6 were converted smoothly to a 1:1 mixture of syn- and anti-4-(pyrrolidino-methylidene)-bicyclo[3.1.0]hex-2-ene (syn- and anti-7-pyrrolidino-homofulvene1) 8 and 9. The structures of 8 and 9 were derived from spectral data. This corrects a previous interpretation by Cook et al.The endo → exo-aminal isomerization (4 → 6) is considered to occur via the enamine (5) of bicyclo[3.1.0]hex-2-ene-6-carbaldehyde (3 or 7), with which the aminals (4 and 6) are in equilibrium. The same enamine (5), a methylidene cyclopropane derivative, is thought to be the intermediate in the aminal (4 or 6) → amino-homofulvene (8 and 9) conversion, which, therefore, belongs to the vinyl-methylidene-cyclopropane rearrangement type.A cationic mechanism for the endo → exo-aminal isomerization is excluded by the discrepancy in this reaction of the pyrrolidino-aminals (13 and 15) of 6-exo-methyl-bicyclo[3.1.0]hex-2-ene-6-endo-carbaldehyde (12) and of bicyclo[3.1.0]hexane-6-endo-carbaldehyde (14). While the former aminal (13) is stable even under acid catalysis and at higher temperatures, the latter (15) isomerizes readily to the exo-aminal 16.The three endo-aldehydes 3, 12 and 14 were prepared by the alkali catalyzed rearrangement of the three chlorohydrins 7-endo-chloro-bicyclo[3.2.0]hept-2-en-6-endo-ol (20ac), 7-endo-chloro-7-exo-methyl-bicyclo[3.2.0]hept-2-en-6-endo-ol (20ad) and 7-endo-chloro-bicyclo[3.2.0]heptan-6-endo-ol (20bc) according to the method of Brook.The configurations of the unsaturated endo-aldehydes 3 and 12 followed from their equilibria with the corresponding 2-oxa-bicyclo[3.2.1]octa-3,6-diene systems (23) and those of the saturated aldehydes 14 and 17 from oxidations to the corresponding carboxylic acids. The endo- and exo- isomers of the aldehydes and aminals treated in this work were readily distinguished by certain highly characteristic NMR.-signals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19740570327
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    The structure of Arteannuin B and its Acid Hydrolysis Product (1974)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 57 (1974), S. 602-615 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die Struktur des Sesquiterpen-γ-Laktons Arteannuin B (1) wurde röntgenographisch und diejenige seines Hydrolyseproduktes (2) durch eine vollständige Analyse des NMR.-Spektrums ermittelt.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19740570314
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...