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.