ALUMINUM-CHLORIDE CATALYZED STEREOSPECIFIC AND REGIOSPECIFIC ALLYLSILYLATION OF ALKYNES - A CONVENIENT ROUTE TO SILYLDIENES

Allyltrimethylsilane reacts with phenylalkynes in the presence of alum inum chloride catalyst under mild conditions to afford silylphenyldien es in moderate yield. In this allylsilylation reaction, the silyl grou p adds regioselectively to the terminal carbon and the allyl group to the inner carbon of the triple bond. The allylsilylation of phenylacet ylene gives the allylsilylated product having the silyl and allyl grou ps in the cis-position, while diphenylacetylene gives the trans produc t. The allylic inversion was also observed in the allylsilylation with the stereohomogeneous (Z)-crotyltrimethylsilane. These results are co nsistent with the initial formation of trimethylsilyl cation intermedi ate and a stepwise process of allylsilylation.