Scheme 1:

Conjugate reduction of 1a with P(O)NNP(O) Lewis Base catalysts. Reaction conditions: 1a (0.27 mmol), HSiCl₃ (1.35 mmol), catalyst (0.027 mmol) in CH₂Cl₂ at 0 °C for 20 h. Conversion of 1a to 2a, and enantioselectivity were analyzed on SFC at 220 nm UV wavelength with a chiral stationary phase. (a) Application of BIBOPO catalyst; (b) rational design of new catalysts; (c) synthesis and evaluation of the new catalysts. ^aReaction was running in acetonitrile.