Enantioselective Trifunctional Organocatalysts for Rate- Enhanced Aza-Morita–Baylis–Hillman Reactions at Room Temperature

✍ Scribed by Jean-Marc Garnier; Christopher Anstiss; Fei Liu

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 364 KB
• Volume: 351
• Category: Article
• ISSN: 1615-4150
• DOI: 10.1002/adsc.200800679

✦ Synopsis

Abstract

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A Brønsted acid‐activated trifunctional organocatalyst, based on the BINAP scaffold, was used for the first time to catalyze aza‐Morita‐Baylis–Hillman reactions between N‐tosylimines and methyl vinyl ketone with fast reaction rates and good enantioselectivity at room temperature. This trifunctional catalyst, containing a Lewis base, a Brønsted base, and a Brønsted acid, required acid activation to confer its enantioselectivity and rate improvement for both electron‐rich and electron‐deficient imine substrates. The role of the amino Lewis base of 1a was investigated and found to be the activity switch in response to an acid additive. The counterion of the acid additive was found to influence not only the excess ratio but also the sense of asymmetric induction.