C₃‐Symmetrical Cinchonine‐Squaramide as New Highly Efficient, and Recyclable Organocatalyst for Enantioselective Michael Addition

Abstract

A novel and recyclable catalyst, a C 3 -symmetrical cinchonine-squaramide, has been developed for the asymmetric Michael addition of 1,3-dicarbonyl compounds to nitroalkenes. When using only 1 mol% of catalyst 1a for the reaction, high reaction yields with excellent enantioselectivities and diastereoselectivities (up to 96% yield, > 99% ee, > 99:1 dr) were achieved, in which the results for cyclic keto esters are the best ever achieved. Moreover, 1a can be easily recovered by simple precipitation and was used for six cycles without losing any selectivity and activity.

Solid state structural relation and binary melting phase diagram of (S-) and racemic 2-(2-nitro-1-phenylethyl)-1,3-diphenyl-propane-1,3-dione

“…The most common way of its synthesis is the asymmetric Michael addition of 1,3-diphenylpropane-2,5-dion (2) to a trans--nitrostyrene (3) in the presence of a chiral catalyst (Scheme 1).…”

Applications of Chiral Squaramides: From Asymmetric Organocatalysis to Biologically Active Compounds

“…Among them, the C 3 -symmetrical cinchonine-squaramide (CSCS) (Figure 2) is one of the most elegant organocatalysts, which has exhibited excellent enantioselectivity in various asymmetric transformations. [13][14][15] Building on their previous success with the C 3 -symmetric chiral cinchonine-squaramide (CSCS), they further expanded this squaramide organocatalyst in asymmetric Friedel-Crafts reactions of indole and alkyl trifluoropyruvate. A wide variety of trifluoromethylated indole derivatives were achieved in Xin Han was born in 1987 in Henan province, China.…”

C3-Symmetric cinchonine-squaramide as a recyclable efficient organocatalyst for tandem Michael addition–cyclisation of malononitrile and nitrovinylphenols

“…[8][9][10][11][12] We have developed a series of novel chiral squaramide organocatalysts; the C 3 -symmetric cinchonine-squaramide (CSCS) catalyst was one of the most useful organocatalysts, which showed remarkable behavior in asymmetric Michael additions, Friedel-Crafts reactions and asymmetric halolactonisations as well. [13][14][15] On the other hand, 2-amino-4H-chromene derivatives showed anticancer, antimitotic microtubule and anti-Alzheimer's disease activity. [16][17][18][19] Therefore, the development of effective protocols to access enantiomerically pure 2-amino-4H-chromene derivatives for further pharmaceutical investigation is highly desirable.…”