General procedure for the synthesis of methyl 2,3-diaminobenzoate from methyl 2-amino-3-nitrobenzoate: to a nitrogen-saturated solution of methyl 2-amino-3-nitrobenzoate (Chess GmbH, 50 g, 0.26 mol) in anhydrous ethanol (800 mL) was added palladium hydroxide (Degussa, 20% w/w carbon, 58.75% w/w water. 10g). The mixed slurry was degassed and stirred vigorously at room temperature under hydrogen (4 atm) atmosphere for 48 hours. Upon completion of the reaction, the catalyst was removed by filtration and the filtrate was concentrated under vacuum to give methyl 2,3-diaminobenzoate as a dark orange oil, which solidified to a solid after standing (43 g, 0.26 mol, 100% yield). Mass spectrometry analysis (m/z): calculated value of [M-OCH3]+ C8H10N2O2 was 135.05; measured value was 135.3.1H NMR (300 MHz, DMSO-d6) data: δ (ppm) 3.74 (s, 3H), 4.80 (br s, 1H), 6.20 (br s, 1H), 6.38 (t, 1H). 6.70 (d, 1H), 7.06 (d, 1H).
