Enantioselective Synthesis of Chromanones through Organocatalytic Tandem Reactions

Abstract An enantioselective approach to lactone‐fused chromanone derivatives from 1‐(2‐hydroxyaryl)‐1,3‐diketones and α,β‐unsaturated aldehydes under mild conditions has been developed, which included organocatalytic stepwise Michael addition/ cycloketalization/hemiacetalization and followed by oxidation reaction. In the presence of chiral amine organocatalyst and an additional salicylic acid, a wide range of 1‐(2‐hydroxyaryl)‐1,3‐diketones and α,β‐unsaturated aldehydes were tolerated, furnishing a spectrum of lactone‐fused tricyclic chromanones bearing three contiguous stereocenters in high yields with good to excellent selectivities (90‐>99% ee, >19:1 d.r.). magnified image