Seung Ho Yeon

Aluminum chloride catalyzed stereo- and regiospecific allylsilylation of alkynes: a convenient route to silyldienes

Abstract Allyltrimethylsilane reacts with phenylalkynes in the presence of aluminium chloride catalyst under mild conditions to afford silylphenyldienes in moderate yield. In this allylsilylation reaction, the silyl group adds regioselectively to the terminal carbon and the allyl group to the inner carbon of the triple bond. The allylsilylation of phenylacetylene gives the allylsilylated product having the silyl and allyl groups in the cis -position, while diphenylacetylene gives the trans product. The allylic inversion was also observed in the allylsilylation with the stereohomogeneous ( Z )-crotyltrimethylsilane. These results are consistent with the initial formation of trimethylsilyl cation intermediate and a stepwise process of allylsilylation.

EFFECTS OF HYDROGEN CHLORIDE ADDITION TO THE DIRECT REACTION OF METHYLENE CHLORIDE WITH ELEMENTAL SILICON

Abstract Direct synthesis of bis(chlorosily)methanes has been reinvestigated by reacting elemental silicon simultaneously with methylene chloride and hydrogen chloride in the presence of copper catalyst using a stirred reactor equipped with a spiral band agitator at a carefully controlled temperature between 260 and 340°C. Bis(dichlorosily)methane and (dichlorosily)(trichlorosily)methane were obtained as the major products and bis(trichlorosily)methane as a minor product along with trichlorosilabe and tetrachlorosilane derived from the reaction between elemental silicon and hydrogen chloride. The decomposition of methylene chloride was suppressed and the production of polymeric carbosilanes reduced by adding hydrogen chloride to the methylene chloride reactant. The optimum mixing ratio of methylene chloride and hydrogen chloride for the direct synthesis of bis(silyl)methanes was 1:4. The deactivation problem of elemental silicon owing to decomposition of methylene chloride and polycarbosilanes was eliminated. Cadmium was a good promoter for the reaction, while zinc was found to be an inhibitor for this particular reaction.

Hydrosilylation of Olefins with Allyldichlorosilane: A Convenient Route to Allyl Group Containing Organodichlorosilanes

The hydrosilylation of olefins with allyldicholorosilane in the presence of chloroplatinic acid diluted with isopropanol gave allylalkyldichlorosilanes, retaining the allyl group. When the olefin was used in fivefold excess or more relative to allyldichlorosilane, allylalkyldichlorosilanes were obtained in good yields (63–89%), and the formation of double hydrosilylation products was reduced to less than 6%. The isomerization of allylsilane to 1-propenylsilane was suppressed by lowering reaction temperatures below 100°C. This hydrosilylation of olefins with allyldichlorosilane is a good synthetic route to an allyl group containing organodichlorosilanes.