Bismuth Triflate-L(-)-Proline Catalyzed Synthesis of Chiral 2,5-Diaryl-2,3-dihydropyrano[2,3-b]quinolin-4-ones

The synthesis of chiral (2R) 2,5-diaryl-2,3-dihydropyrano[2,3-b]quinolin-4-ones, was achieved, at ambient temperature, by the reaction of 3-acetyl-4-aryl-carbostyril and an aldehyde, in the presence of bismuth triflate-L(-)-proline complex, formed in situ. The products were obtained in 62-78% yield with high enantioselectivity (72-96% ee).