Highly Efficient Phosphine-Free Pd(OAc)2-Catalyzed Fukuyama Coupling Reaction: Synthesis of a Key Intermediate for (+)-Biotin under Low Catalyst Loading

A phosphine-free catalytic system involving inexpensive Pd(OAc)2 in conjunction with Zn dust and ZnBr2 was unexpectedly found to effect the Fukuyama coupling reaction of thiolactone 2 with zinc reagent 3 to provide vinyl sulfide 6, a key intermediate for (+)-biotin (1), in high yield with a very tiny amount of Pd (up to 0.01 mol%, TON = 6800).