4,5-Diamino-2-(2-chloro-phenylamino)-3-fluoro-benzoic acid methyl ester 6a (0.125 g, 0.404 mmol) is suspended in EtOH (2 mL) and formamidine acetate (63 mg, 0.605 mmol) is added. The reaction mixture is heated to reflux. After 16 hours, the reaction mixture is cooled to room temperature and diluted with ethyl acetate. The organic layer is washed with water, saturated NaHCO3, 10% K2CO3 and brine. The organic layer is dried (MgSO4) and concentrated under reduced pressure to give 0.109 g (85%) pure desired product.
