Highly regioselective thiocarbonylation of allylic alcohols with thiols and carbon monoxide catalyzed by palladium complexes:: A new and efficient route to β,γ-unsaturated thioesters

The reaction of allylic alcohols with thiols and carbon monoxide in the presence of catalytic quantities of Pd(OAc)(2) (3 mol %), triphenylphosphine (12 mol %), and p-TsOH (5 mol %) leads to a novel thiocarbonylation to afford beta,gamma-unsaturated thioesters in good to excellent yields. Other palladium catalyst systems such as Pd-2(dba)(3). CHCl3-PPh3-p-TsOH, Pd(PPh3)(4)-p-TsOH, and Pd(OAc)(2)-dppb-p-TsOH are also effective for this transformation. The thiocarbonylation reaction is believed to proceed via a allylpalladium intermediate. The reaction occurs highly regioselectively at the least hindered allylic terminal carbon of the substrate to give the products. This new carbonylation procedure was readily applied to a variety of allylic alcohols and both aromatic and aliphatic thiols.