Chiral Squaramide Derivatives are Excellent Hydrogen Bond Donor Catalysts

By J. Malerich, Koji Hagihara, V. Rawal. Journal of the American Chemical Society, 2008

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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 β-nitrostyrenes. The addition products were obtained in high yields and excellent enantioselectivities.

Subfields: Organic Chemistry

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