Chiral Silver Complex-Catalyzed Asymmetric Conjugate Addition of 1-Pyrroline-5-Carbonitrile to α-Enones.

The conjugated addition reaction of 1-pyrroline-5-carbonitrile to α-enones was effectively catalyzed by AgF/ThioClickFerrophos (TCF) in diethyl ether in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and nearly single diastereomers of adducts with good enantiomeric excesses (up to 97% ee) were obtained in high yields. The reduction of the nitrile group with H 2 /Raney Ni in ethanol successfully transformed the conjugate adduct to the corresponding spirocyclic piperidine (60% yield) as a single stereoisomer.