Thiourea axial chiral derivatives

Kim and coworkers have developed a binaphthyl-modified chiral squaramide (20) bearing both central and axial chiralities [89]. The Michael addition of anthrone to nitroalkenes catalyzed by squaramide 20 afforded the products in high yield and good enantioselectivity (Scheme 10.17). Notably, the reaction at lower temperature (0 °C) resulted in a reduced enantioselectivily. This transformation has also been shown to be catalyzed by cinchona alkaloid and thiourea derivatives [90-92]. 

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