Diethyl Ether → Methyl 7-fluoro-6-(2-methyl-phenylamino)-benzo[1,2,5]thiadiazole-5-carboxylate

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Reaction Steps

To a stirring solution comprised of methyl 4,5-diamino-3-fluoro-2-(2-methyl-phenylamino)-benzoate (from Step e, Example 1) and diisopropylethylamine (2 equiv.) in an appropriate solvent like diethyl ether or toluene is added a reagent like N-thioaniline or thionyl chloride (1.35 equiv.). The reaction mixture is brought to reflux for one hour. The mixture is quenched with dilute aqueous hydrochloric acid. The organic phase is washed with saturated aqueous sodium bicarbonate and brine, is dried (MgSO4), and is concentrated in vacuo to afford the desired product. The product may be recrystallized with an appropriate solvent like chloroform or ethanol, or may be chromatographed if further purification is necessary.

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