Chiral squaramide derivatives are excellent hydrogen bond donor catalysts.
Thioureas represent the 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 squaramide (5), easily prepared through a two-step process from methyl squarate, was shown to be an effective catalyst, even at catalyst loadings as low as 0.1 mol%, for the conjugate addition reactions of 1,3-dicarbonyl compounds to beta-nitrostyrenes. The addition products were obtained in high yields and excellent enantioselectivities.
Malerich
Jeremiah P
JP
Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, USA.
Hagihara
Koji
K
Rawal
Viresh H
VH
D000577:Amides / Q000737:chemistry*; D002384:Catalysis; D002930:Cinchona Alkaloids / Q000737:chemistry; D003503:Cyclobutanes / Q000737:chemistry*; D006860:Hydrogen Bonding; D007659:Ketones / Q000138:chemical synthesis / Q000737:chemistry*; D009574:Nitro Compounds / Q000138:chemical synthesis*; D010420:Pentanes / Q000737:chemistry; D013343:Styrenes / Q000737:chemistry*
D000577:Amides; D002930:Cinchona Alkaloids; D003503:Cyclobutanes; D007659:Ketones; D009574:Nitro Compounds; D010420:Pentanes; D013343:Styrenes; C011955:beta-nitrostyrene; C030042:squaric acid; C010086:cinchonine