Ammonium Chloride → 5-Chloropyrazinamide

Participants

Reaction Conditions

Reaction Steps

Suspend ammonium chloride (0.465 g, 8.69 mmol) in toluene (14 mL). Cool to 0° C. and slowly add 2.0 M Al(CH3)3 in toluene (4.3 mL, 8.69 mmol). After the gas stops evolving, add 5-chloropyrazine-2-carboxylic acid methyl ester (0.500 g, 2.89 mmol). Heat at 50° C. overnight. Cool the reaction mixture to room temperature, then slowly pour into a slurry of silica gel (10 g) in CHCl3 (50 mL). Stir for 10 minutes before filtering. Wash the silica plug with methanol (2×100 mL) before concentrating. Take the resulting solid up in dichloromethane and wash with water (30 mL) and brine (40 mL). Dry the organic layer over Na2SO4, filter and concentrate. Purify by flash chromatography, eluting with 50% ethyl acetate in hexanes to give the title compound (0.155 g, 34.0%): TOF MS EI+ 157.0 (M+), HRMS calcd for C5H4N3OCl 157.0043 (M+H)+, found 157.0047, time 4.19 min; HPLC [YMC-Pack Pro C-18 (150×4.6 mm, S-5 microm), 0.1% TFA/acetonitrile in 0.1% TFA/water at 1.0 mL/min. 5-95% over 19 min], tR=7.1 min, 100% purity.

Provenance & Evidence