Asymmetric synthesis of fused seven-membered chromanones from 3-hydroxy chromones and vinyl ethylene carbonates.

A practical and efficient protocol for the enantioselective synthesis of seven-membered fused chromanone derivatives has been developed under mild conditions. This approach proceeds via a stepwise sequence involving a palladium-catalyzed O-allylic reaction of 3-hydroxy chromones with vinyl ethylene carbonates, followed by a copper-promoted asymmetric [1,3]-rearrangement/hemiketalization cascade. The method exhibits broad substrate tolerance, affording the new chromanone products in moderate yields with excellent enantio- and diastereoselectivities (19-76% yield, 89-97% ee, >19 : 1 dr).