Enantioselective Michael Addition of Pyrazolin-5-ones to Nitroalkenes Catalyzed by Novel Squaramide Organocatalyst

A new tertiary amine-thiourea organocatalyst has successfully been developed and applied into the asymmetric Michael addition of pyrazolin-5-one to nitroalkenes. The catalyst system performed well with a low catalyst loading of 5 mol% under mild reaction conditions. A series of synthetically and pharmaceutically useful chiral pyrazolone derivatives was obtained in high yields (up to 95%) with good enantioselectivities (up to 88 % ee).