Condensation chlorure d'acide-organomagnesien en presence d'halogenure cuivreux: Competition des reactions heterolytique et homolytique. synthese de cetones aliphatiques ramifiees

The reactivity of seven sterically hindered acid chlorides RCOCl towards ethylmagnesium bromide in the presence of cuprous chloride has been studied. In addition to the ketones RCOEt, the compounds RCOCOR, RCOR, RR, RH and R(H) are produced by a radical reaction. The condensation of R′MgX with iPr₂CHCOCl in the presence of cuprous halide proceeds via alkylcopper species R′Cu.MgXX′ which reacts with the acid chloride to produce the ketone RCOR′. The radical process is initiated by the decomposition of the alkylcopper intermediate. The effect of temperature, solvent and structure on the stability of the alkylcopper on optimal conditions for ketonisation has been studied; this is demonstrated specifically by the synthesis of 9 hindered ketones iPr₂CHCOR′, where Me? R′ ? Et₃C and Tr.