An organocatalytic asymmetric double Michael cascade reaction of unsaturated ketones and unsaturated pyrazolones : highly efficient synthesis of spiropyrazolone derivatives

摘要

The first organocatalytic double Michael cascade reaction between unsaturated ketones and unsaturated pyrazolones has been developed which provides spiropyrazolone core structures containing two interval or three consecutive stereogenic centers with excellent diastereo- (>20:1) and enantioselectivities (up to 99% ee). Moreover, a pair of enantiomers 5 and 5′ can be achieved via different catalysts.