Highly regioselective thiocarbonylation of conjugated dienes via palladium-catalyzed three-component coupling reactions

Three-component coupling reaction of conjugated dienes, thiols, and carbon monoxide affords an atom-economical thiocarbonylation of the dienes to give beta,gamma-unsaturated thioesters as the sole products. A catalyst system based on [Pd(OAc)(2)] and Ph3P showed excellent catalytic activity. The thiocarbonylation was performed under an atmosphere of carbon monoxide (400 psi) at 110 degrees C in CH2Cl2 for 60 h. A wide variety of thioesters were synthesized in good to excellent yields from easily accessible starting materials. The reaction is believed to proceed via a eta(3)-allylpalladium intermediate. The thiocarbonylation, which is applicable to a nide variety of conjugated dienes, occurs in high regioselectivity, the latter dependent on the steric characteristics and stability of the eta(3)-allylpalladium complex.