Gold-mediated synthesis of α-ionone

A simple and convenient synthesis of α-ionone, an important component of flowers and fragrances, is reported. The key step in the formation of the α,β-unsaturated ketone moiety involves an NHC-AuI catalyzed Meyer–Schuster-like rearrangement of readily prepared propargylic esters. The complex [{Au(IPr)}2(μ-OH)][BF4] proved to be the most efficient catalyst leading to α-ionone in 70% yield from a propargylic benzoate. This optimized procedure represents a valuable and attractive alternative to classical methods leading to α,β-unsaturated ketones, such as the Wittig or aldol reactions.