Two-step allylic carbon insertion between ketone carbonyl and α carbons giving α-quaternary α-vinyl ketones

Ketones 1 were converted to α-quaternary α-vinyl ketones 2 by a two-step formal allylic carbon insertion between ketone carbonyl and α carbons, which involves the reaction of 1 with propargyltitanium reagents, derived from propargyl carbonates 3 and a divalent titanium reagent Ti(O-i-Pr)4/2i-PrMgCl, and the following rearrangement of the resulting α-allenyl alcohols 4 with NBS.

Ketones 1 were converted to α-quaternary α-vinyl ketones 2 by reaction with propargyltitanium reagents, derived from propargyl carbonates 3 and a divalent titanium reagent, followed by rearrangement of the resulting α-allenyl alcohols 4 with NBS.