Liquid-phase organic reactions catalyzed by inorganic solid acids and bases

Abstract

CaO and MgO as strong solid bases catalyzed the regio- and chemoselective ring opening of epoxides with Me 3SiCN at room temperature much more efficiently than homogeneous promoters. On CaO and MgO, the reactions of unsymmetrical epoxyalkanes with Me 3SiCN afforded exclusively 3-trimethylsiloxy-alkanenitriles in high yields. On CaO, 2,3-epoxy-1-alkanol derivatives were selectively converted to the corresponding C-3 opening products. Both strong solid bases (MgO, CaO, and hydroxyapatite) and strong solid acids (Al 3+-and Fe 3+-exchanged montmorillonites) catalyzed the cyanosilylation of carbonyl compounds with Me 3SiCN regioselectively. On CaO, α,β-unsaturated ketones were cyanosilylated to give the 1,2-adducts selectively, while the solid acids gave the 1,4-adducts selectively. Hydrosilylation of carbonyl compounds with hydrosilanes was also efficiently catalyzed by solid acids and bases. Enones are selectively hydrosilylated over hydroxyapatite to afford the corresponding 1,2-adducts in high yields. Thus the solid acids and bases appear to be highly pertinent as catalysts to the activation of carbonyl compounds or epoxides and organosilane nucleophiles, respectively.