REDUCTION OF CARBONYL-COMPOUNDS WITH HYDROSILANES ON SOLID ACID AND SOLID BASE

Hydrosilylations of carbonyl compounds were performed on the surfaces of solid acids and bases. Strongly acidic clays efficiently catalyzed the reduction of aldehydes and ketones with trialkylsilanes (e.g. Et3SiH) to afford symmetrical ethers or hydrocarbons, depending upon the characters of substituents around carbonyl groups. Reduction-resistant ketone like 4,4'-dimethoxybenzophenone was found to be reduced with Et3SiH under the catalytic influence of the highly acidic clay. In contrast, trialkoxysilanes (e.g. (EtO)3SiH) became labile in contact with solid base like hydroxyapatite, reducing a variety of carbonyl compounds to yield alkoxy(triethoxy)silane in good yields. It was revealed that besides fluoride sats, solid bases bearing mild basicity and relatively large surface areas can activate the trialkoxysilane enough for reduction of carbonyl functions.