Rhodium-catalyzed isomerization of 1,3-diene monoepoxides to α,β-unsaturated carbonyl compounds

Article abstract of DOI:10.1016/0022-328X(89)85435-X

α,β-Unsaturated aldehydes and ketones are readily formed by the rhodium(I) catalyzed isomerization of 1,3-diene monoepoxides.When RhH(PPh3)4 is used as a catalyst, only (E)-α,β-unsaturated carbonyl compounds are obtained selectively.The initial 1,3-diene monoepoxides are prepared regiospecifically from α-trimethylsilyl ketones by a two step procedure, bromination and subsequent vinylative epoxidation of resulting α-bromo ketones.The overall transformation from α-trimethylsilyl ketones to α,β-enones is formally regarded as an equivalent of the regiospecific aldol condensation, and also enables the use of unsymmetrically substituted ketones as an enolate source.The significance of the isomerization as a key step in the synthesis of ar-turmerone is described.