Titanium-Catalyzed Formal Dihydroacylation of Terminal Alkynes

A titanium-catalyzed formal dihydroacylation of terminal alkynes is reported. The new process, in which the alkynes are directly converted into saturated aryl ketones, is based on an initial regioselective hydroaminoalkylation with a secondary benzylamine, a subsequent double-bond isomerization of the initially formed allylamine, and a final imine hydrolysis. The entire hydroaminoalkylation–hydrolysis sequence proceeds smoothly with variously substituted N-benzylanilines, but is limited to terminal alkynes without propargylic hydrogen atoms.