Cinchona-based primary amine-catalyzed asymmetric cascade aza-Michael-aldol reactions of enones with 2-(1H-pyrrol-2-yl)-2-oxoacetates: synthesis of chiral pyrrolizines with multistereocenters.

ABSTRACT

Cinchona-based primary amine-catalyzed cascade aza-Michael-aldol reactions of α,ß-unsaturated ketones with 2-(1H-pyrrol-2-yl)-2-oxoacetates provided highly functionalized chiral pyrrolizines bearing multistereocenters including a chiral quaternary carbon center in good yields (up to 92%) with excellent levels of stereocontrol (90-95% ee, >201 dr in all cases). The ketone group in the cascade product was asymmetrically reduced to chiral secondary hydroxyl groups in good yields.