10H-pyrido(3,2-b)(1,4)benzothiazine

95873-97-5

261-96-1

General procedure for the synthesis of azaphenothiazine from the compound (CAS: 95873-97-5): 15.0 g (119.82 mmol) of intermediate (C) was suspended with 4.36 g (119.82 mmol) of hydrochloric acid in 470 mL of ethanol and the reaction was carried out at reflux for 12 h at 70 °C under nitrogen protection. After completion of the reaction, extraction was carried out with dichloromethane and distilled water and the organic layer was filtered through silica gel. After concentrating the organic solvent, it was purified by silica gel column chromatography (eluent: ethyl acetate/petroleum ether = 7:3, v/v) to give 20.64 g of intermediate (D) in 86% yield.