2.1 Synthesis of 2-naphthylhydrazine hydrochloride
To a hydrochloric acid solution of 2-naphthylamine (800 mg, 5.59 mmol), a solution of sodium peroxide (Na?O?, 578 mg, 8.38 mmol) in water (1.2 mL) was slowly added under water-ice bath cooling conditions (addition time: 2 min). Subsequently, 6.0 M hydrochloric acid (6 mL) was added to the reaction system. The resulting solution was stirred in a water-ice bath for 1 h. Stannous chloride (SnCl?, 3.71 g, 19.56 mmol) was then slowly added (addition time: 5 min). The resulting suspension was continued to be stirred in a water-ice bath for 3.5 h, after which it was filtered. The filter cake was washed sequentially with water at 0 °C (4 × 8 mL), water at room temperature (1 × 8 mL), ether at 0 °C (Et?O, 2 × 4 mL), ether/hexane (1:1, 2 × 4 mL) and hexane (2 × 5 mL). The solid was dried to give 690 mg of the target product (Rf = 0.7, 40% ethyl acetate/hexane unfolding agent, milky white solid, 63% yield).
1H NMR (DMSO-d6, 250 MHz, δ): 7.81 (m, 2H, ArH), 7.71 (d, J=7.5 Hz, 1H, ArH), 7.49-7.19 (m, 4H, ArH).
MS-EI+ m/z: 159.1 ([M-HCl]+).
