Practical Synthesis of Linear α-Iodo/Bromo-α,β-unsaturated Aldehydes/Ketones from Propargylic Alcohols via Au/Mo Bimetallic Catalysis

An efficient synthesis of alpha-iodolbromo-alpha,beta-unsaturated aldehydes/ketones directly from propargylic alcohols is described. This reaction is catalyzed collaboratively by two metal complexes, Ph3PAuNTf2 and MoO2(acac)(2), and Ph3PO as an additive helps suppress undesired enone/enal formation. Notable features of this method include low catalyst loadings, mild reaction conditions, and mostly good to excellent diastereoselectivity. In comparison with our previously developed method based on propargylic acetate substrates, this chemistry omits the need to prepare acetate derivatives and, moreover, has a much broader substrate scope.