Enantioselective elimination reaction of a 6,6-membered bicyclic allylic carbonate, importance of chirality reversal depending on the palladium-chiral phosphine ratio.

Reaction of (+/-)-8 alpha-methoxycarbonyloxy-4a beta-methyl-2,3,4,4a,5,6,7,8-octahydronaphthalene (1) in the presence of a palladium-chiral phosphine catalyst gave 4a-methyl-3,4,4a,5,6,7-hexahydronaphthalene (2) enantioselectively. When the reaction was carried out using Pd(OAc)(2) and (S)-(-)-BINAP, the enantioselection was influenced by the phosphine to palladium ratio, because (S)-BINAP oxide generated in situ acted as a ligand causing the opposite enantioselectivity. High enantioselectivity (86% ee) was obtained when (1-Me-C3H5-PdCl)(2) and (S)-(-)-p-Tol-BINAP were used. Copyright (C) 1996 Elsevier Science Ltd