A New Methodology for the Synthesis of Enones

Abstract

In connection with other work, we had a need to make large amounts of 4,4-diphenyl-3-buten-2-one (1). Many good and general methods exist¹ for making enones; we wish to describe a new sequence of old reactions to make desired enones that doesn't appear in the recent compilations of synthetic methods.² The method involves the Reformatsky condensation of propargyl bromide with a ketone or aldehyde, followed by an acid catalyzed rearrangement to the enone. The rearrangement is related to the well-known acid catalyzed Rupe rearrangement³ of alpha-hydroxyacethylenes to enones, which presumably proceeds via an intermediate vinyl-acetylene.⁴