Cesium carbonate → 7-bromo-2-ethyl-4H-benzo[1,4]thiazin-3-one

Participants

Reaction Steps

To a mixture of 2-amino-5-bromo-benzenethiol (20 g, 0.1 mol) and cesium carbonate (33 g, 0.1 mol) in DMF (500 ml) at −35° C. was added dropwise 2-bromobutyrylbromide (23 g, 0.1 mol). The mixture was allowed to warm to room temperature, poured into ice/water, and extracted with CH2Cl2 (2×50 mL). The combined organic extracts were washed with water, then brine, dried (MgSO4) and evaporated. The residue was purified by column chromatography (SiO2, ethyl acetate:hexane/1:6) to afford 7-bromo-2-ethyl-4H-benzo[1,4]thiazin-3-one (3.7 g, 14%): mp 100° C.; MS (EI) m/z 271/273(M+).

Provenance & Evidence