Asymmetric α-Amination of Aldehydes Catalyzed by PS-Diphenylprolinol Silyl Ethers: Remediation of Catalyst Deactivation for Continuous Flow Operation
作者:Xinyuan Fan、Sonia Sayalero、Miquel A. Pericàs
DOI:10.1002/adsc.201200887
日期:2012.11.12
diphenylprolinol silylethers have been developed as highly active catalysts for the enantioselective α-amination of aldehydes. Understanding the mechanism of catalystdeactivation has led to the development of reaction conditions notably extending catalyst life in repeated recycling (10 cycles; accumulated TON of 480) and has allowed the implementation of a continuousflowα-amination process (6 min
Pyrrolidine-derived organocatalysts were tested in two types of α-heterofunctionalization reactions in aqueousmedia or under solvent-free ball-milling conditions. The best results in terms both activity and enantioselectivity were obtained with O-silylated 4-hydroxyproline derivatives in the α-aminoxylation reaction between n-butyraldehyde and nitrosobenzene (83% yield for water, 86% yield for ball
The asymmetricα-amination of aldehydes was performed using a resin-supportedpeptidecatalyst. A tri- or tetrapeptide with an N-terminal D-Pro-Aib sequence efficiently catalyzed the reaction in a highly enantioselective manner. The supported catalyst could be easily recovered by filtration and reused at least ten times.