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Enantioselective Cyanosilylation of Ketones by a Catalytic Double‐Activation Method with an Aluminium Complex and an N‐Oxide
Author(s) -
Chen FuXue,
Zhou Hui,
Liu Xiaohua,
Qin Bo,
Feng Xiaoming,
Zhang Guolin,
Jiang Yaozhong
Publication year - 2004
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200400506
Subject(s) - lewis acids and bases , chemistry , cyanohydrin , catalysis , ketone , enantioselective synthesis , organic chemistry , medicinal chemistry
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.