Asymmetric Addition of Pyrazolones to Allenamides Catalyzed by a Chiral Phosphoric Acid

We describe a new asymmetric allylic alkylation of pyrazolones, in which an all-carbon quaternary stereocenter with broad substrate scope and good enantioselectivity was generated. The asymmetric addition of pyrazolones to allenamides could be carried out under mild conditions in excellent yields with a relatively low catalyst loading. The allylic products with an enamide structure can be easily transformed to the pyrazolones with other functional groups, which provides a new approach for the asymmetric introduction of new functional groups into the pyrazolone skeleton.