Chiral Silver Complex-Catalyzed Diastereoselective and Enantioselective Michael Addition of 1-Pyrroline-5-carboxylates to α-Enones

A AgOAc/ThioClickFerrophos complex-catalyzed the highly diastereo- and enantioselective reaction between 1-pyrroline-5-carboxylates (1) and acyclic α-enones (2) in MeOH, in the presence of DBU, to give the single isomer Michael adducts (3) in high yields (up to 99%) with excellent enantioselectivies (up to 99% ee). Subsequent reduction of the Michael adducts with sodium cyanoborohydride successfully produced the fused pyrrolizidine ester as an almost pure single stereoisomer.