Asymmetric Halocyclization of 2-Anilidostyrenes Using N-Haloamides Enabled by Chiral Anion Phase-Transfer Catalysis

Asymmetric halogenation for efficient construction of various 4H-3,1-benzoxazine derivatives with excellent functional group tolerance using readily available N-haloamides as the halogen source and ammonium phosphate salt catalyst under mild reaction conditions has been developed. The ammonium salt catalyst loading could be reduced to 1 mol % and recycled 4 times without deterioration in reactivity and stereoselectivity. Importantly, this process features a column-purification-free operation, leading to the green and atom-economical preparation of chiral benzoxazines in good to excellent yields and high enantioselectivities.