Synthesis of N-Boc-cyclopropylhydrazine:
Cyclopropylamine (59.3 g, 1.04 mol, 10 eq.), dichloromethane (180 mL), and N-methylmorpholine (NMM, 11.5 g, 0.114 mol, 1.1 eq.) were added sequentially to a 500 mL three-necked flask, and the reaction was cooled down to -5~0 C in an ice-salt bath with the addition in batches of solid N Boc-O-tosylhydroxylamine (BocHNOTs, 29.8 g, 0.104 mol, 1.0 eq.), after addition, the reaction was maintained at 0 C to continue for 2 h. The reaction was followed by TLC to monitor the reaction endpoint at room temperature (below 20 C) overnight. Stop the reaction, concentrate dry, add dichloromethane and water to the crude product, after layering, collect the organic phase, the aqueous layer was then extracted twice with dichloromethane, combine the organic phases, drying, filtration, concentrated to obtain the crude product (21g, theoretical 16.4g), the crude product was pulped with petroleum ether to obtain a light yellow solid (11g, 67% yield), melting point 105.4~106.2C.
Preparation of cyclopropylhydrazine hydrochloride:
To a 100 mL three-necked flask was added N-Boc-cyclopropylhydrazine (5 g, 29 mmoL, 1.0 eq.), and concentrated hydrochloric acid (10 mL) was added dropwise in an ice-water bath. After dropping, the reaction was carried out at room temperature (20~25C) overnight (17~20 hours), the end of the reaction was monitored by TLC tracking, the reaction solution was decolorized by the addition of activated charcoal, filtered, and the aqueous phase was concentrated to obtain 10g of crude product, which was recrystallized from ethanol to obtain white crystals (2.4g, 76% yield), melting point 131.6~132.6C.
