A New Enantioselective Approach to the Bicyclo[4.4.0]decane and Bicyclo[4.3.0]nonane Systems

Abstract

Highly diastereoselective routes to cis-fused bicyclo[4.4.0]decane-2,10-diones and bicyclo[4.3.0]nonane-2,9-diones from 5-trimethylsilyl-2-cyclohexen-1-one (1a) and its 3-methyl derivative were established by utilizing an annulation with ω-(alkoxycarbonyl)alkylzinc reagents. Bicyclo[4.4.0]decane-2,8-dione was obtained diastereoselectively by the double Michael reaction of 1a with dienol silyl ether. The diastereoselective Diels–Alder reaction of 1a with cyclopentadiene gave an endo adduct, which can be regarded as a new chiral cyclohexenone synthon, with a high optical purity.

Stereochemical Control in Organic Synthesis Using Silicon-Containing Compounds

“…The adduct 405 can be used to prepare the cyclohexenone 406 that is formally an adduct of the cyclohexadienone tautomer of phenol. This adduct can be used to reinstate a 5-substituted cyclohexenone 408 , but with a different group in place of the original silyl group, by taking advantage of the reversibility 407 → 408 of the Diels−Alder reaction (Scheme ) 92 …”

“…This adduct can be used to reinstate a 5-substituted cyclohexenone 408, but with a different group in place of the original silyl group, by taking advantage of the reversibility 407 f 408 of the Diels-Alder reaction (Scheme 92). 214 In heterocyclic system 409, conjugate addition is not quite so regular, with the reagent making a surprising and unexplained difference to the sense of the stereoselectivity. The copper-catalyzed methyl Grignard reagent gave the expected product 410, with the incoming group anti to the silyl group, but the phenyl Grignard gave the unexpected diastereoisomer 411.…”

Efficient Syntheses of the OPC Homologous Series, OPC-1:0, -3:0, -4:0, -5:0, -6:0, -7:0, and-8:0

“…8) Zinc-copper reagents (8a-8f), which had been generated from the corresponding iodo-esters (7a-7f) by the method of Asaoka et al,9) were subjected to 1,4-conjugate addition to 4. In order to optimize the reaction conditions, the stoichiometry of the zinc-copper reagents and the reaction temperature were varied.…”

The Concept of Transient Chirality in the Stereoselective Synthesis of Functionalized Cycloalkenes Applying the Retro-Diels−Alder Methodology

“…So far all the examples mentioned above have dealt with racemic material, and it is obvious that full advantage of the concept of transient chirality is obtained when access to the diene adducts can be accomplished in an enantioselective manner for the ultimate preparation of enantiomerically pure cyclohexenoids. A first approach constitutes the asymmetric Diels−Alder reaction of enantiopure 5-trimethylsilylcyclohexenone 208 with cyclopentadiene catalyzed by aluminum chloride (Scheme ) . A mixture of endo - and exo- adduct 209 is obtained in 83% yield with an endo/exo ratio of 13.5:1.…”