Novelbifunctionalchiralsquaramide–amine organocatalysts have been developed by rational combination of pyrrolidine and a cinchona alkaloid. The catalysts promoted the enantioselective Michael addition of both mono- and diketones to a broad range of nitroalkenes providing the corresponding products in moderate to high yields with excellent enantioselectivities and diastereoselectivities (up to 96%
A Polystyrene-Supported, Highly Recyclable Squaramide Organocatalyst for the Enantioselective Michael Addition of 1,3-Dicarbonyl Compounds to β-Nitrostyrenes
作者:Pinar Kasaplar、Paola Riente、Caroline Hartmann、Miquel A. Pericàs
DOI:10.1002/adsc.201200526
日期:2012.11.12
A chiral squaramide has been supported onto a polystyrene (PS) resin through a copper-catalyzed azide–alkyne cycloaddition (CuAAC) reaction and used as a very active, easily recoverable and highly reusable organocatalyst for the asymmetric Michaeladdition of 1,3-dicarbonylcompounds to β-nitrostyrenes. The PS-supported squaramide could be recycled up to 10 times.
Chiral Squaramide Derivatives are Excellent Hydrogen Bond Donor Catalysts
作者:Jeremiah P. Malerich、Koji Hagihara、Viresh H. Rawal
DOI:10.1021/ja805693p
日期:2008.11.5
dominant platform for hydrogen bond promoted asymmetric catalysts. A large number of reactions, reported in scores of publications, have been successfully promoted by chiral thioureas. The present paper reports the use of squaramides as a highly effective new scaffold for the development of chiral hydrogen bond donor catalysts. Squaramide catalysts are very simple to prepare. The (-)-cinchonine modified
Highly efficient and enantioselective Michael addition of acetylacetone to nitroolefins catalyzed by chiral bifunctional organocatalyst bearing multiple hydrogen-bonding donors
作者:Xin Shi、Wei He、Hua Li、Xu Zhang、Shengyong Zhang
DOI:10.1016/j.tetlet.2011.04.043
日期:2011.6
efficient catalyst system for the asymmetric addition of acetylacetone to nitroolefins using a chiral bifunctionalorganocatalyst bearing multiple hydrogen-bonding donors was developed. When using the organocatalyst 2c derived from natural cinchona alkaloid in optimal conditions, up to 98% chemical yield and 98% ee were observed with a variety of aromatic nitroolefins.