Enantioselective Cyanosilylation of Ketones by a Catalytic Double‐Activation Method with an Aluminium Complex and an N‐Oxide
- 22 September 2004
- journal article
- research article
- Published by Wiley in Chemistry – A European Journal
- Vol. 10 (19), 4790-4797
- https://doi.org/10.1002/chem.200400506
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.Keywords
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