Highly chemo- and regioselective thiocarbonylation of conjugated enynes with thiols and carbon monoxide catalyzed by palladium complexes: An efficient and atom-economical access to 2-(phenylthiocarbonyl) 1,3-dienes

The reaction of 1,3-conjugated enynes bearing a terminal triple bond, e.g., H2C:CMeC≡CH, with thiols, e.g., PhSH, and CO in the presence of catalytic amt. of Pd(OAc)2 and 1,3-bis(diphenylphosphino)propane in THF at 110° gave 2-(phenylthiocarbonyl) 1,3-dienes, e.g., MeC(:CH2)C(:CH2)COSPh, in moderate to good yields. The thiocarbonylation takes place with high chemo- and regioselectivity, with the attack by the phenylthiocarbonyl group occurring exclusively at C-2 of the 1,3-conjugated enyne.