Enantioselective Palladium/Organo-Catalyzed Additions to Unsaturated Aldehydes
Synergistic Catalysis: Enantioselective Addition of Alkylbenzoxazoles to Enals.
Chem. Eur. J. 2014;
15 December 2014 (online)
Synergistic catalysis has recently been gaining attention because the two separate catalysts can be optimized independently (see Review below). The authors present a palladium/chiral secondary amine catalyzed reaction between azaarenes and unsaturated aldehydes.
A. E. Allen, D. W. C. MacMillan Chem. Sci. 2012, 3, 633–658.
Although diastereoselectivity was poor (highest ratio 2.7:1), good enantioselectivities were observed for both major and minor isomers. The palladium acts as a Lewis acid to activate the azaarene, whereas the proline-derived organocatalyst activates the aldehyde towards 1,4-addition.