Versatile method for introduction of bulky substituents to alkoxychlorosilanes

The reactions of various alkoxytrichlorosilanes prepared in situ from tetrachlorosilane and alcohols, with Grignard reagents bearing a bulky substituent such as the isopropyl, sec-butyl, and cyclohexyl group afforded triisopropyl-, tri(sec-butyl)-, and tricyclohexylalkoxysilane in high yields. The reactions of n-butoxytrichlorosilane with these Grignard reagents produced triisopropyl-, tri(sec-butyl)-, and tricyclohexyl(n-butoxy)silane in 94%, 96%, and 92% yields, respectively. Methoxymethyldichlorosilane reacted with the same Grignard reagents to give diisopropyl-, di(sec-butyl)-, and dicyclohexylmethoxymethylsilane in 84%, 83%, and 83% yields. Treatment of methoxydimethylchlorosilane with the Grignard reagents readily afforded isopropyl-, sec-butyl-, and cyclohexylmethoxydimethylsilane in excellent yields. Similar treatment of methoxydimethylchlorosilane with tert-butylmagnesium chloride gave tert-butylmethoxydimethylsilane in 62% yield.