Synthesis of 2-substituted 3,4-dihydro-2H-1,4-benzoxazines through ligandless copper-catalyzed cyclization of hydroxysulfonamides under phase-transfer catalysis conditions

The ring closing under solid–liquid phase-transfer catalysis conditions (SL-PTC) of hydroxysulfonamides 7, bearing a leaving group in the ortho position of the aryl moiety, generates 2-substituted-3,4-dihydro-2H-1,4-benzoxazines 4 in good to excellent yields. In the case of hydroxysulfonamides 7 bearing a bromine or iodine atom as a leaving group, a copper(I) salt is used to enable the reaction to occur.

Graphical abstractThe ring closing under solid–liquid phase-transfer catalysis (SL-PTC) conditions of hydroxysulfonamides 7, bearing a leaving group in the ortho position of the aryl moiety, generates benzoxazines 4 in good to excellent yields. In the case of hydroxysulfonamides 7 bearing a bromine or iodine atom as a leaving group, a copper(I) salt is used.Figure optionsDownload full-size imageDownload as PowerPoint slide