Preparation of 1,4-Dihydroquinolines Bearing a Chiral Sulfoxide Group: New Highly Enantioselective Recyclable NADH Mimics

The stereoselective preparation of 1,4-dihydroquinolines possessing a chiral sulfoxide group at C-3 is reported. These novel biomimetic NADH models (R)-1a,b have been shown to be highly enantioselective in the reduction of methyl benzoylformate, producing (R)-methyl mandelate in up to 95% ee. The corresponding quinolinium salts 4a,b have been recovered in good yields. The regenerated models 1a,b could be reused without any significant erosion of the enantioselectivity.