Further studies on palladium-catalyzed bismetallative cyclization of enynes in the presence of Bu3SnSiMe3

Bismetallative cyclization of enynes with Bu3SnSiMe3 catalyzed by Pd(0) complex was realized for the first time, which gives cyclized products containing a vinylsilane moiety and a homoallyltin moiety in good yield. In this cyclization, Pd2(dba)3·CHCl3 or Pd(OH)2 on charcoal is effective as a Pd(0) catalyst and the addition of a phosphine ligand increased the formation of alkyne bismetallation by-product. On the other hand, it was found that a nucleophilic N-heterocyclic carbene could be utilized as a ligand for this cyclization. The utility of the cyclized products obtained from this cyclization in synthetic organic chemistry have been proven by transformation into cyclopropanol derivatives.