Pd-catalyzed relay Heck arylation of alkenyl alcohols with arylsulfonium salts

Abstract

A palladium-catalyzed tandem Heck arylation and isomerization of alkenyl alcohols using arylsulfonium salts is reported. The reaction enabled facile conversion of various allylic and non-allylic alcohols to the corresponding arylalkyl ketones or aldehydes in good to excellent yields. Different types of arylsulfonium salts were verified as powerful arylation reagents in the relay Heck reactions via chain-walking without being affected by the sulfide byproducts. The transformation exhibited obvious advantages such as high efficiency, mild conditions, good functional group tolerance, excellent regioselectivity, and a wide range of substrates, which allowed remote functionalization of alkenyl alcohols with more complex aryl transfer reagents. A plausible reaction mechanism was presumed to involve the initial Heck arylation of the alkenyl moiety with arylsulfonium salts, repeated migratory insertion and β-hydride elimination, and enol isomerization to yield the final product. Moreover, the Pd-catalyst remains coordinated to the substrate during the relay process. This work represents the first remote functionalization of alkenyl alcohols with arylsulfonium salts as the arylation reagents.