Anionotropic Rearrangements of 3-Bromo-1-(2-nitrophenyl)propan-1-ols and Their Esters in Fluorosulfonic Acid

Kinetically controlled reaction of 3-bromo-1-(2-nitrophenyl)propan-1-ols and their formic acid esters with fluorosulfonic acid afforded 3-(2-bromoethyl)-1-oxo-1,3-dihydro-2,1-benzoxazol-1-ium and 6-bromo-3-(2-bromoethyl)-1-oxo-1,3-dihydro-2,1-benzoxazol-1-ium fluorosulfonates. As the reaction mixture was kept at 20°C, these ions underwent anionotropic rearrangements leading to the formation of 3-bromomethyl-1-oxo-3,4-dihydro-1H-2,1-benzoxazin-1-ium, 4-bromo-3-methyl-1-oxo-3,4-dihydro-1H-2,1-benzoxazin-1-ium, and 5-bromo-1-oxo-1,3,4,5-tetrahydro-2,1-benzoxazepin-1-ium fluorosulfonates. The complete transformation was achieved in 84 h after dissolution of the initial 3-bromo-1-(2-nitrophenyl)propan-1-ols or their esters.