REGIOCONTROL BY ANCHIMERIC COORDINATION IN THE REACTIONS OF ORGANOCOPPER REAGENTS WITH ALLYLIC SUBSTRATES BEARING 2 LEAVING GROUPS - SYNTHESIS OF OPTICALLY-ACTIVE HOMOALLYLIC ALCOHOLS

The regiochemistry in the reactions of organocopper reagents with allylic electrophiles bearing two different leaving groups has been studied. Sulphide ester like 4 react with organocopper reagents through regioselective substitution of the sulphide group to give esters of homoallylic alcohols. This regiocontrol is due to the anchimeric co-ordination exerted towards the organometallic reagent by the heterocyclic sulphide. By using sulphide ester 8, whose heterocyclic moiety is optically active, the anchimeric co-ordination allows the synthesis of optically active esters of homoallylic alcohols. The regiocontrol is completely lost if cuprates are used as nucleophiles.