Stereospecific syntheses of the α-patchoulene and α-cedrene skeletons from a common intermediate

Deslongchamps, Pierre; Lafontaine, J.; Ruest, Luc; Soucy, Pierre

doi:10.1139/v77-584

Cited by 4 publications

References 10 publications

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Intramolecular Reactions of Diazocarbonyl Compounds

Burke

Grieco

1979

Organic Reactions

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Since the demonstration by Stork and Ficini in 1961 that unsaturated diazoketones undergo intramolecular cyclization to form cyclopropanes the intramolecular reactions of α‐diazocarbonyl compounds have been extensively studied under thermal, catalytic, and photochemical conditions. Intramolecular cyclization of α‐carbonyl carbenes and carbenoids has found widespread application to the synthesis of theoretically interesting compounds such as bullvalene, twistane, bridged annulenes, and barbaralone, as well as syntheses of natural products such as sabinene, sirenin, α‐chamigrene, and phyllocladene. The reaction has also allowed the construction of several intriguing polycyclic systems that were unattainable by alternative methods. A recent review has covered the reactions of diazoacetic esters with alkenes, alkynes, heterocyclics, and aromatic compounds. Unsaturated alkoxycarbonyl carbenes (:CHCO 2 R) and unsaturated carbonyl carbenes (:CHCOR) (where R contains either aromatic or olefinic groups), which are considered to be intermediates in the absence of catalyst, have been the subject of several other reviews. A review concerning photochemically, thermally, and catalytically induced Wolff rearrangements of α‐diazocarbonyl compounds has recently appeared. However to date no comprehensive review has appeared which demonstrates the synthetic potential of α‐diazocarbonyl insertion and addition reactions. In reviewing the reactions of α‐diazocarbonyl compounds chosen not to include certain peripheral topics such as intermolecular reactions, intramolecular dimerization of bis(α‐carbonyl carbenoids) to give diacyl cycloolefins and intramolecular trimerizations of tris(α‐keto carbenoids), affording triacylcyclopropanes are not included. Also excluded are base‐catalyzed reactions of α‐diazocarbonyl compounds and certain ring‐contraction reactions involving CC bond insertion of intermediate α‐ketocarbenes. The topics included in this report are the intramolecular reactions of α‐carbonyl carbenes and carbenoids with olefinic and aromatic unsaturation, with CH bonds, and with CC and NH single bonds. Also included are acid‐catalyzed cyclization reactions of α‐diazoketones.

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Intramolecular Reactions of Diazocarbonyl Compounds

Burke

Grieco

1979

Organic Reactions

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ChemInform Abstract: STEREOSPECIFIC SYNTHESES OF THE α‐PATCHOULENE AND α‐CEDRENE SKELETONS FROM A COMMON INTERMEDIATE

Deslongchamps¹,

Lafontaine²,

Ruest³

et al. 1978

Chemischer Informationsdienst

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Two‐dimensional NMR studies of cyperene

et al. 1984

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Combined utilization of 'H-IH homonuclear and 'H-l'C heteronuclear N M R chemical shift correlations,two-dimensional J-resolved 'H NMR measurements and homonuclear 'H double resonance experiments allowed specific assignments for both 'H and -C NMR frequencies to be made for the tricyclic sesquiterpene cyperene. The results also provided information on the conformation of the six-membered ring of this natural product, which was recognized as a distorted chair.Cyperene (1) is a tricyclic monounsaturated hydrocarbon of pleasant odour originally isolated from Cyperus1 and, more recently, from Perezia.' Its structure is closely related to that of a -and y-patch~ulenes,'~~ constituents of the fine perfume of patchouli the only difference being the position of the double bond, which is located6 between carbons 4 and 5 in CYpatchoulene and as an exocyclic methylene group at C-4 in y-patchoulene. Two other related molecules, @-and 6 -p a t~h o u l e n e ,~~~ have the 4,7-methanoazulene skeleton"' instead of the 3a,7-methanoazulene framework present in cyperene (1) and in a -and y -patchoulenes. Owing to the close structural relationship of cyperene to the highly expensive and widely appreciated patchoulenes, and the fact that cyperene analogues have already been found as minor constituents in plant m a t e r i a l~, l "~~~-~~ it seemed desirable to undertake detailed NMR studies of the more easily accessible cyperene. These studies might be of further utility for the structural elucidation of other closely related natural products. RESULTS ~The detailed assignment of both the 'H and I3C NMR spectra of cyperene is difficult since, on the one hand, the twelve 'H methylene and methine signals are found between 1.1 and 2.7ppm and, on the other, in the 13C spectrum four methylene signals appear within a range of only 2ppm. Further, since three of these methylene signals are within a very narrow range of only 0.82 ppm, and sp3-sp3 one-bond carbon-carbon coupling constants are of the orderc6 of 35 Hz, the use * Authors to whom correspondence should be addressed.of double quantum coherence17 measurements is not recommended since, in such cases,l* strongly coupled AB systems with distorted intensities arise.Therefore, the 'H and 13C spectral parameters for cyperene were deduced from both heteronuclearl' (lH-13C) and homonuclear2' (lH-lH) chemical shift correlations, and several coupling constants were obtained from the homonuclear J-resolved'l 'H NMR spectrum and from one-dimensional 'H measurements with the aid of spin-spin decoupling experiments, which also provide information on the conformation of the six-membered ring of the natural product 1.Preliminary information about the number of directly attached protons to each sp3 carbon atom was obtained from two APT (attached proton test) experi-

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Stereospecific syntheses of the α-patchoulene and α-cedrene skeletons from a common intermediate

Cited by 4 publications

References 10 publications

Intramolecular Reactions of Diazocarbonyl Compounds

Intramolecular Reactions of Diazocarbonyl Compounds

ChemInform Abstract: STEREOSPECIFIC SYNTHESES OF THE α‐PATCHOULENE AND α‐CEDRENE SKELETONS FROM A COMMON INTERMEDIATE

Two‐dimensional NMR studies of cyperene

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