An enantiospecific cobaloxime π-cation initiated carbocyclisation

The cationic carbocyclisation of the allyl silane substituted beta-hydroxycobaloxime (+)-4 was effected by treatment with catalytic amounts of pTSA to form the cyclopentane derivative (+)-5 which was elaborated to the aldehyde (-)-7 via the alcohol (-)-6. Both the optical rotation of (-)-7 and the ee of (-)-6 determined by Mosher esterification revealed that (+)-5 had been formed in an enantiospecific fashion with retention of configuration at the inducing stereogenic centre. (C) 1998 Elsevier Science Ltd. All rights reserved.