Intercepting the gold-catalysed Meyer–Schuster rearrangement by controlled protodemetallation: a regioselective hydration of propargylic alcohols

The regioselective gold-catalysed hydration of propargylic alcohols to beta-hydroxy ketones can be achieved by diverting the gold-catalysed Meyer–Schuster rearrangement through the addition of a protic additive with a pKa of 7–9 such as para-nitrophenol, boric acid or a boronic acid. This provides an interesting alternative to an aldol reaction when combined with the straightforward addition of an alkyne to an aldehyde or ketone. The gold-catalysed reaction of an electron-deficient, sterically hindered propargylic alcohol with a boronic acid led to the formation of an unusually stable cyclic boron enolate.