Triethyl phosphite → 5-Bromo-6-chlorobenzo[c][1,2,5]oxadiazole

Participants

Reaction Steps

6-Bromo-5-chlorobenzo[c][1,2,5]oxadiazole 1-oxide (4.8 g, 19 mmol) was taken up 150 ml ethanol, heated to reflux, treated with triethyl phosphite (8.8 g, 53 mmol) and heated for 3.5 h. After cooling, the volatiles were removed by rotary evaporation, the residue was taken up in 100 mL dichloromethane and stirred with 50 mL bleach solution for 30 min. The organic phase was washed with 20 mL saturated NaCl, dried (Na2SO4) and evaporated. The crude material was purified by flash chromatography with a 0-30% ethyl acetate-hexane gradient to give the title compound as an orange solid (3.5 g, 79%): mp 68-69° C.; 1H NMR (400 MHz, CDCl3) δ 8.30 (s, 1H), 8.05 (s, 1H); EIMS m/z 232.

Provenance & Evidence