Selective Transformation of β‐Disubstituted Enones and Ynones in the Presence of β‐Monosubstituted Enones

Abstract α,β‐Unsaturated carbonyl groups are found in many natural products and functional molecules. The reactivity of nucleophiles towards α,β‐unsaturated carbonyls, such as β‐monosubstituted and disubstituted α,β‐unsaturated ketones (enones) and ynones, is similar. Therefore, the development of a method to selectively convert α,β‐unsaturated carbonyls is desirable. In this study, selective one‐pot reductions and allylations of β‐disubstituted enones or ynones were accomplished in the presence of β‐monosubstituted enones using an in situ protection methodology. β‐Monosubstituted enones selectively reacted with a combination of triphenylphosphine and trimethylsilyl triflate in the presence of β‐disubstituted enones or ynones to produce phosphonium silyl enol ethers, which acted as enone protecting groups during the reduction and allylation of the remaining β‐disubstituted enone or ynone. The substrate was then easily deprotected in the workup to regenerate the parent enone.