Cationic Rhodium Complex-Catalyzed Hydrosilylation of a,P-Unsaturated Carbonyl Compounds: Stereoselective Synthesis of Acyclic Silyl Enol Ethers

摘要

Silyl enol ethers are one of the most important organosilicon compounds. For example, they could be used for Mukaiyama aldol reaction. General synthetic method for silyl enol ethers is a reaction of metal enolate with chlorosilane, but in this method, the formation of a stoichiometric amount of metal chloride is accompanied. Another.synthetic method for silyl enol ethers is a regioselective 1,4-hydrosilylation of alpha,beta-unsaturated ketone. The reaction is atom-economical and environmental benign. 1,4-Hydrosilylation of cyclic enones has been reported by some groups. The reaction of acyclic enones gives a mixture of the (E)- and (Z)-silyl enol ethers. The control of stereoselectivity in the acyclic silyl enol ether formation has scarcely been studied. We found that the 1,4-hydrosilylation of acyclic enones in the presence of a catalytic amount of cationic rhodium complex proceeded to give (Z)-siIyl enol ethers in high yields with high regio- and stereoselectivities (eq 1).