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

Ketones 1 were converted to of-quaternary of-vinyl ketones 2 by a two-step formal allylic carbon insertion between ketone carbonyl and alpha 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 alpha-allenyl alcohols 4 with NBS. (c) 2008 Elsevier Ltd. All rights reserved.