Synthesis of 7-bromotryptamine HCl
To a stirred suspension of 2-bromophenylhydrazine hydrochloride (25.8 g, 115 mmol) in chloroform (500 mL) was added saturated sodium carbonate solution (500 mL). The mixture was stirred for 30 minutes and extracted with chloroform (2×200 mL). The combined organic phases were concentrated to afford the hydrazine free base as a yellow oil. This oil was dissolved in methanol (100 mL) and treated slowly with 4-chlorobutanal (12.3 g, 115 mmol). The mixture was placed in a sealable tube and purged with nitrogen for 10 minutes. The tube was sealed and placed in an oil bath preheated to 95°C. Heating was continued for 18 hours. The resulting dark solution was cooled to ambient temperature and concentrated under reduced pressure. The residue was partitioned between chloroform/methanol (75/25 by volume) and aqueous sodium carbonate solution. The organic phase was concentrated and the crude tryptamine was purified by flash chromatography on silica gel (0-25% methanol gradient in chloroform as eluent). Fractions containing product were combined and concentrated. The oil was dissolved in diethyl ether (300 mL) containing 1% methanol and treated with dry HCl gas. The hydrochloride salt was isolated by filtration, washed with 2-propanol (50 mL) and diethyl ether (100 mL) and dried to afford 7-bromotryptamine hydrochloride (3.6 g) as a pale solid.
References
[1] US Pat 5508284
