32315-10-9

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321-50-6

Step A- Synthesis of intermediate compound Int-4a: To a solution of 2-amino-4-fluorobenzoic acid (15.5 g, 100 mmol) in tetrahydrofuran (THF, 200 mL) was slowly added triphosgene (27.9 g, 105 mmol) at 0 °C. The reaction mixture was warmed up to 50 °C with continuous stirring for 6 hours. Upon completion of the reaction, the solvent was removed by distillation under reduced pressure. The resulting crude product was ground with a solvent mixture of ethyl acetate/petroleum ether (1:1, v/v) and the solid was collected by filtration to afford the intermediate compound Int-4a (15.7 g, 85% yield). The product was characterized by 1H NMR (400 MHz, DMSO-d6): δ 11.9 (s, 1H), 7.95-7.98 (m, 1H), 7.06-7.11 (m, 1H), 6.84-6.89 (m, 1H).