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  • Title: Enantioselective cyanosilylation of ketones by a catalytic double-activation method with an aluminium complex and an N-oxide.
    Author: Chen FX, Zhou H, Liu X, Qin B, Feng X, Zhang G, Jiang Y.
    Journal: Chemistry; 2004 Oct 04; 10(19):4790-7. PubMed ID: 15372678.
    Abstract:
    Double-activation catalysis promises high catalytic efficiency in the enantioselective cyanosilylation of ketones through the combined use of a Lewis acid and a Lewis base. Catalyst systems composed of a chiral salen-Al complex and an N-oxide have high catalytic turnovers (200 for aromatic ketones, 1000 for aliphatic ones). With these catalysts, a wide range of aliphatic and aromatic ketones were converted under mild conditions into tertiary cyanohydrin O-TMS ethers in excellent yields and with high enantioselectivities (94% ee for aromatic ketones, 90% ee for aliphatic ones). Preliminary mechanistic studies revealed that the salen-Al complex played the role of a Lewis acid to activate the ketone and the N-oxide that of a Lewis base to activate TMSCN; that is, double activation.
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