Synthesis
General procedure for the synthesis of methyl 3-amino-5-nitrobenzoate from methanol and 3-amino-5-nitrobenzoic acid: The esterification reaction was carried out by passing dry hydrogen chloride gas into a solution of methanol (160 ml) containing 5-amino-3-nitrobenzoic acid (18.5 g, 0.10 mol). After the solution was saturated, the reaction mixture was stirred at room temperature overnight. Subsequently, the mixture was concentrated to a crystalline residue. The residue was dissolved in dichloromethane and washed with 5% sodium bicarbonate solution until the pH of the aqueous phase reached 7-8. The organic phase was separated, dried over magnesium sulfate and evaporated to remove the solvent. The product 18.6 g was obtained in 94% yield.1H NMR (CDCl3) data: δ 8.21 (t, 1H, J=1.5Hz), 4.19 (br s, 2H), 3.96 (s, 3H).
References
[1] Organic Letters, 2013, vol. 15, # 17, p. 4442 - 4445
[2] Patent: WO2007/29587, 2007, A1. Location in patent: Page/Page column 35
[3] Patent: WO2007/55580, 2007, A1. Location in patent: Page/Page column 16
[4] Patent: EP1953163, 2008, A1. Location in patent: Page/Page column 12
[5] Patent: WO2004/50619, 2004, A1. Location in patent: Page 16
