Methanol → 2-Cyclopropylamino-4,5-difluorobenzoic acid methyl ester

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Reaction Steps

To a solution of 2-cyclopropylamino-4,5-difluorobenzoic acid (Example 5a) (6.0 g, 28.1 mmol), dichloromethane (100 mL), and methanol (20 mL) is added (trimethylsilyl)diazomethane (2.9 M solution in hexane) dropwise until the evolution of gas stops. The solution is stirred at room temperature for 0.5 hour and 88% formic acid is added dropwise until the evolution of gas again stops. Water is added, and the solution is extracted with dichloromethane, dried over MgSO4, filtered, and the solvent removed under reduced pressure. The residue is purified by silica gel column chromatography using hexane/EtOAc (9:1) as the eluent afford a 5.4 g of the title compound as a clear oil. MS CI: m/z 228 (MH+).

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