Step 1: Synthesis of ethyl 4-hydrazinobenzoate hydrochloride. A concentrated hydrochloric acid solution of ethyl 4-aminobenzoate (2 g, 12.181 mmol) was stirred and cooled at -20 °C. To this solution was slowly added aqueous sodium nitrite (925 mg, 13.40 mmol) in 22 mL of concentrated hydrochloric acid. The above mixture was slowly added dropwise to a pre-cooled (-10°C) solution of tin chloride (13.8 g, 60.905 mmol) in hydrochloric acid (15 mL). Stirring of the reaction mixture was continued at the same temperature for 30 minutes. Upon completion of the reaction, the precipitate was collected by filtration and washed with ether (2 x 20 mL) to afford 2.2 g of the target product ethyl 4-hydrazinylbenzoate hydrochloride as an off-white solid. The product was characterized by 1H NMR (300 MHz, DMSO-d6): δ1.29 (t, J=7.2 Hz, 3H), 4.26 (q, J=7.5 Hz, 2H), 6.99 (d, J=7.8 Hz, 2H), 7.87 (d, J=8.4 Hz, 2H), 8.95 (br s, 1H), 10.48 (br s, 2H) ; APCI-MS (m/z) 181 (M+H)+.
