p-Toluenesulfonic acid → Methyl 3-bromo-2-fluorobenzoate

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Reaction Steps

A solution of 3-bromo-2-fluorobenzoic acid (0.219 g, 1 mmol) in dry methanol (5 mL) under nitrogen was treated with trimethylorthoformate (0.22 mL, 2 mmol) and p-toluenesulfonic acid (catalytic amount), and then heated under reflux. After 16 h, the mixture was evaporated and the residue partitioned between water and Et2O. The organic layer was washed with sat. sodium hydrogen carbonate solution, water, brine, dried (MgSO4) and evaporated to give methyl 3-bromo-2-fluorobenzoate (0.195 g, 0.84 mmol, 84%): 1H-NMR (CDCl3) δ 7.90-7.85 (m, 1H), 7.71-7.65 (m, 1H), 7.10 (dt, 1H, J=8.0, 1.0 Hz), 3.94 (s, 3H): MS (EI) 232 (M+).

Provenance & Evidence