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 Nbenzylanilines, but is limited to terminal alkynes without propargylic hydrogen atoms.
Thye et al. (Tue,) studied this question.