Mild Direct Remote Hydroxylation of Enals in Air

A mild direct remote hydroxylation of α,β-unsaturated aldehydes is reported. Air is the oxidant, and tertiary alcohol products are generated in up to 80% yield. This method selectively hydroxylates enals with acidic γ-carbons and therefore may be suitable for late-stage installation of remote hydroxyl groups on medicinal aldehydes. Mechanistic studies that enabled the development of this transformation are described, as is the first example of catalytic enantioselective γ-hydroxylation of an enal.