Pyrrolidines cinchonine-squaramide

Subsequently, several groups have studied related squaramide-catalyzed enantioselective Michael addition of 1,3-dicarbonyl compounds to nitroalkenes. High enantioselectivities have been achieved using pyrrolidine-cinchonine-squaramide catalyst 14 [81], quinine-squaramide catalyst 15 [82, 83], and Cs-symmetrical cinchonine-squaramide catalyst 16 (Figure 10.4) [84]. Notably, the reaction time... 

Dong and coworkers have developed a pyrrolidine-cinchonine-squaramide catalyst for enantioselective Michael addition of ketones to nitroalkenes (Scheme 10.16) [81]. The assembly of two privileged chiral motifs, pyrrolidine and cinchonine, with a squaramide core enabled the catalyst in promoting the addition of both cyclohexanone and 1,3-diketones to aryl-substituted nitroalkenes, providing the corresponding products in modest to high diastereo- and enantioselectivities. The authors pointed out that the match between the chiralities of pyrrolidine and cinchonine is important for the high enantioselectivity. 

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See also in sourсe #XX -- [ ]

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