Enantioselective Organocatalytic Synthesis of δ‐Lactone‐Fused 4‐Chromanones

Abstract

AbstractAn organocatalytic enantioselective synthesis of δ‐lactone‐fused 4‐chromanones was demonstrated using 1‐(2‐hydroxyaryl)‐1,3‐butanedione and α,β‐unsaturated aldehydes in the presence of the Jørgensen‐Hayashi catalyst. The reaction proceeded through a Michael addition/cycloketalization/hemiacetalization sequence, and the resulting hemiacetals were oxidized into the corresponding lactone derivatives in a one‐pot manner. The desired fused O,O‐ketal tricyclic lactone motifs containing three contiguous chiral centers were obtained in excellent chemical yields (up to 97%) and with high stereoselectivities (up to >20:1 dr and up to 95% ee).magnified image