Titanocene(III) chloride mediated radical-induced addition to Baylis-Hillman adducts: synthesis of (E)- and (Z)-trisubstituted alkenes and alpha-methylene/arylidene delta-lactones.

Baylis-Hillman adduct underwent smooth radical-induced condensation with activated bromo compounds and epoxides using titanocene(III) chloride (Cp2TiCl) as the radical generator. The reactions of activated bromo compounds with 3-acetoxy-2-methylene alkanoates provided (E)-alkenes exclusively, whereas similar reactions with 3-acetoxy-2-methylenealkanenitriles led to (Z)-alkenes as the major product. The reactions of epoxides with Baylis-Hillman adduct furnished alpha-methylene/arylidene-delta-lactones in good yield via addition followed by in situ lactonization.