Regiospecific Homologation of Unsymmetrical Ketones

Article abstract of DOI:10.1021/jo00163a034

A method has been developed for the regiospecific homologation of unhindered unsymmetrical ketones.The procedure consists of preparation of a pure α-halo ketone, reaction of this derivative with ethyl diazoacetate and boron trifluoride etherate, removal of the halogen by zinc reduction, and finally decarbethoxylation with water at 230 deg C or with CaCl2*2H2O in dimethyl sulfoxide at 150 deg C.The method depends on the electron-withdrawing power of the α-halogen to prevent the migration of the attached carbon.A-Homo steroid ketones are most conveniently prepared by this method.The reaction of α-acetoxy ketones with ethyl diazoacetate also leads mainly to migration of the unsubstituted α'-carbon atom.