Asymmetric cooperative catalysis in the conjugate addition of pyrazolones to nitroolefins and subsequent dearomative chlorination

Over the past decade many bifunctional amine-thioureas have been developed as active metal-free organocatalysts. Coopera-tive catalysis of these amino-thioureas allows high reaction rates and excellent transfer of stereocbemical information. Despite these impressive advances, the design of new high-performance catalysts for applications in asymmetric catalytic reactions is of ongoing interest in organic chemistry. Herein we describe a cooperative catalyst system consisting of a chiral amine thiourea and an achiral organic acid that promotes the conjugate addition of 4-nonsubstituted pyrazolones to nitroolefins and subsequent dearomative chlorination. The corresponding adducts and the subsequent products were obtained in high to excel lent yields （up to 99%） and high stereoselectivities （up to 99/1 dr, 98% ee） under mild reacton conditions. These transforma tions provide an easy access to enantio-enriched pvrazole derivatives, which could possess Potential oharmaceutical activity.