Organocatalytic Asymmetric Oxa-Michael-Michael Reaction of 3-Aryl-2-Nitroprop-2-Enols with Unsaturated Pyrazolones: Synthesis of Spirotetrahydropyranopyrazolones

An organocatalytic asymmetric oxa-Michael-Michael reaction of 3-aryl-2-nitroprop-2-enols with alkylidene pyrazolones has been developed. This report describes the first use of a 3-aryl-2-nitroprop-2-enol as an O-nucleophile in enantioselective catalysis. With 10 mol% of a quinine-derived squaramide catalyst, a variety of spirotetrahydropyranopyrazolones were obtained in moderate yields, excellent diastereomeric ratios, and high to excellent enantioselectivities under mild reaction conditions.

Automated summary

An organocatalytic asymmetric oxa-Michael-Michael reaction was developed for the synthesis of spirotetrahydropyranopyrazolones. By utilizing a quinine-derived squaramide catalyst, the reaction achieved moderate yields, excellent diastereomeric ratios, and high to excellent enantioselectivities under mild reaction conditions.