A mild and efficient cyanosilylation of ketones catalyzed by a Lewis acid–Lewis base bifunctional catalyst

A new family of bifunctional catalysts (N-oxides–Ti(OiPr)4 (2:1)) containing a Lewis acid and a Lewis base was developed and applied to the catalytic cyanosilylation of ketones. Utilizing rac((1R,2S) and (1S,2R))-1-(2′-pyridylmethyl)-2-diphenylhydroxymethylpyrrolidine N-oxide–titanium (2:1) complex and N-benzyl-diethanolamine N-oxide–titanium (2:1) complex as catalysts, the cyanosilylation products were obtained in 42–97% yield. Based on experimental phenomena and kinetic studies, a catalytic cycle was proposed to explain the remarkable activities of these catalysts. Investigations indicated that rac((1R,2S) and (1S,2R))-1-(2′-pyridylmethyl)-2-diphenylhydroxymethylpyrrolidine N-oxide–titanium (2:1) complex and N-benzyl-diethanolamine N-oxide–titanium (2:1) complex should promote the reaction via a dual activation of the ketone by the titanium and TMSCN by the N-oxide.