Regioselective control using a catalyst switch in the reaction of diarylmethyl chlorides with allyltributylstannane

Regioselective control in the reaction of diarylmethyl chlorides 5a with allyltributyltin is described. The reaction pathway (allylative dearomatization vs cross-coupling) can be easily controlled using different catalysts. When reactions are performed in the presence of Pd2(dba)3 and PPh3, allylative dearomatization proceeds to provide satisfactory yield of the desired products. However, when Cy3P·HBF4 is employed as a catalyst instead of palladium, a Stille-type cross-coupling reaction takes place exclusively to give excellent yields of the corresponding products.