Studies in ferrocene derivatives. VII. The synthesis of ferrocenyl ethylenes via an abnormal Grignard reaction

Abstract

RMgBr reacts normally with acylferrocenes to give the corresponding alcohols. RMgI gives good yields of the most highly substituted ferrocenyl ethylene. In solutions of moderate acid strength, α-ferrocenyl carbonium ions lose a proton to form the substituted alkene rather than undergo nucleophilic attack by water to give the corresponding alcohol. Since the alcohols are more basic than the alkenes, it is possible to devise a general synthesis of ferrocenyl ethylenes by the reaction of any Grignard reagent with an acylferrocene.