Enantioselective Cyanosilylation of Ketones with Amino Acid/BINAP/Ruthenium(II)-Lithium Phenoxide Catalyst Systems

Enantioselective reactions of simple ketones, a,a- and beta,beta-dialkoxy ketones, and a-alkoxy ketones with trimethylsilyl cyanide catalyzed by the bimetallic systems of amino acid/BINAP/ruthenium(II) complexes and lithium phenoxide have been studied [BINAP=2,2'-bis(diphenylphosphino)-1,1'-binaphthyl]. The Ru(PhGly)2(BINAP)-lithium phenoxide system showed high enantioselectivity for the reaction of acetophenone derivatives to afford the cyanated products in up to 90% ee [PhGly=phenylglycinate]. For the cyanosilylation of dialkoxy ketones and a-alkoxy ketones, the Ru(t-Leu)2(BINAP)-lithium phenoxide system exhibited the best catalyst performance to produce the cyanohydrin derivatives in up to 99% ee and 98% ee, respectively [t-Leu=tert-leucinate]. The excellent catalytic activity resulted in complete conversion in the reaction with a substrate-to-catalyst molar ratio (S/C) of 10,000 in the best cases.