Lanthanum Aryloxide/Pybox-Catalyzed Direct Asymmetric Mannich-Type Reactions Using a Trichloromethyl Ketone as a Propionate Equivalent Donor

Abstract

Direct catalytic asymmetric Mannich-type reaction of a trichloromethyl ketone as a propionate equivalent donor is described. A new lanthanum aryloxide−iPr-pybox + lithium aryloxide combined catalyst was the most effective, promoting the reaction of N-2-thiophenesulfonyl imines with the trichloromethyl ketone. syn-Mannich adducts were obtained from various aryl, heteroaryl, alkenyl, and alkyl imines in >99−72% yield, syn/anti of >30:1−8:1, and 98−92% ee (from a propionate equivalent donor) using 2.5−10 mol % catalyst. The Mannich adduct was converted not only into ester but also into useful building blocks.