CHELATION CONTROLLED ALLYLATION OF ALDEHYDES WITH A CHIRAL ALLYLSILYLENE DERIVED FROM (-)-10-PHENYLPINANEDIOL

The chiral allylsilylene prepared from (-)-10-phenylpinanediol reacts with chiral a-alkoxy aldehydes in the presence of stannic chloride to afford homoallylic alcohols with diastereofacial selectivity ratios as high as 100:0. The results are consistent with attack of the allylsil ylene on the less hindered face of the chelated intermediate. Our prel iminary studies on several silylenes prepared from bicyclo[3.1.1] syst ems revealed that substituent effects on the chiral auxiliary and the silicon atom play an important role in the selectivity of these unique compounds.