Titanium(IV) Chloride-Mediated Stereoselective α-Alkylidenation to Efficiently Assemble Multisubstituted 1,3-Dienes

A direct access to multisubstituted 1,3-dienes by α-exclusive alkylidenation of crotonic derivatives has been developed. This protocol, mediated by titanium tetrachloride chelation, features excellent regio- and stereoselectivity, mild reaction conditions, easy operation and wide substrate scope. Conversions of the derived dienes to other useful molecules were also explored.