MECHANISTIC ASPECTS OF REDUCTIONS OF ALLYLIC ETHERS AND ACETATES WITH ORGANOCUPRATES

The rate of substitution to reduction has been investigated for reactions of three phenyl-substituted allylic ethers and the corresponding acetates with EtMgBr plus 10 or 25% copper(I) bromide in THF. It is found that the relative amount of reduction increases with increased electron delocalization in the postulated copper(III)-bound allyl ligand, and is also dependent on the nature of the leaving group; methoxy giving much more reduction product than acetoxy. Furthermore, for one acetate investigated there was more reduction at -65° than at -25°C. The results are interpreted in terms of relative binding strength of allyl ligands to a copper(III) intermediate. © 1979.