General procedure for the synthesis of 1-Boc-2-isopropylhydrazine from tert-butyl 2-(propan-2-ylidene)hydrazinecarboxylate: tert-butyl 2-(propan-2-ylidene)hydrazinecarboxylate (0.51 g, 3.0 mmol) was dissolved in 20 mL of tetrahydrofuran (THF), sodium cyanoborohydride (NaBH3CN, 0.19 g, 3.0 mmol) and a small amount of bromocresol green was added as the indicator. Subsequently, 1.5 mL of THF solution of p-toluenesulfonic acid (0.57 g, 3.0 mmol) was added slowly and dropwise over about 1 hour, maintaining the pH of the reaction system between 3.5 and 5.0. The reaction mixture was continued to be stirred at room temperature for 1 h before the solvent was removed by rotary evaporation. The residue was extracted by partitioning with ethyl acetate (30 mL) and saturated saline. The organic phase was washed sequentially with saturated sodium bicarbonate solution (20 mL) and saturated saline, and then evaporated to dryness. The obtained residue was dissolved in 10 mL of ethanol, 3.6 mL of 1M sodium hydroxide solution (3.6 mmol) was added and stirred at room temperature for 30 min. After completion of the reaction, the solvent was removed by rotary evaporation and the residue was dissolved in ethyl acetate and extracted with water. The organic layer was evaporated under reduced pressure and the residue was purified by column chromatography to afford tert-butyl 2-isopropylhydrazinecarboxylate (0.4 g, 77% yield) using a dichloromethane solution of 5% methanol as eluent. The product characterization data were as follows: melting point 47-49 °C; thin layer chromatography Rf=0.44 (dichloromethane solution of 5% methanol); 1H NMR (300 MHz, CDCl3) δ 6.03 (s, 1H, NH), 3.92 (s, 1H, NH), 3.14 (m, 1H), 1.46 (s, 9H), 1.02 (d, 6H, J=6 Hz); 13C NMR (300 MHz, CDCl3) δ 157.2, 80.8, 51.2, 28.7, 21.0.
