α-Ethynylation reaction of ketones using catalytic amounts of trialkylgallium base

Trialkylgalliums serve as a base to generate enolates from ketones. In the presence of catalytic amounts of a trialkylgallium (20–40 mol %) and 2,6-di(t-butyl)-4-methylpyridine (30–50 mol %), acyclic, and cyclic ketones were ethynylated at the α-carbon with chlorosilylethyne. The selective monoethynylation and diethynylation could be conducted for cyclic ketones by appropriate choices of the conditions, in which the addition of a catalytic amount of butyllithium (20–40 mol %) increased the yield.