[NH2:1][C:2]1[CH:3]=[C:4]([CH:10]=[CH:11][C:12]=1[CH3:13])[C:5]([NH:7][O:8][CH3:9])=[O:6].[N:14]([O-])=O.[Na+].[Sn](Cl)Cl>O1CCOCC1.O.Cl>[NH:1]([C:2]1[CH:3]=[C:4]([CH:10]=[CH:11][C:12]=1[CH3:13])[C:5]([NH:7][O:8][CH3:9])=[O:6])[NH2:14]To a stirred solution of 3-amino-4-methylbenzoic acid 1 (5.64 g, 31.2 mmol, 1.0 eq) in 100 mL of dioxane and 100 mL of water at 0° C. was added 100 mL of conc. HCl followed by the portionwise addition of sodium nitrite (2.82 g, 40.9 mmol, 1.1 eq) as a solid at a rate to control gas evolution and foaming over 45 minutes. A clear brown solution resulted. Anhydrous tin(II)chloride (15.62 g, 83.7 mmol, 2.25 eq) was dissolved in conc. HCl (25 mL) and added dropwise over 25 mL at 0° C. After 1 hour, the precipitate was filtered and washed with dioxanes then dried under vacuum to provide 3-hydrazino-4-methyl-benzoic acid hydrochloride 2 as a tan solid (4.98 g, 66%): HPLC (4 minute gradient) tR 0.97 min; MS m/z 167 [M+H]+; 1H (300 MHz, DMSO-d6) δ 10.03 (s, 1 H, COOH), 7.89 (s, 1 H), 7.51 (s, 1 H), 7.27 (d, J=8.0, 1 H), 3.38 (s, 3 H, NHNH2), 2.23 (s, 3 H) ppm.
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