Synthesis
A mixture of aluminum trichloride (0.17 g, 1.24 mmol) and methanesulfonyl chloride (0.17 mL, 2.34 mmol) in dichloromethane (20 mL) was stirred for 15 min at 0 °C, followed by the addition of 1-(10H-phenothiazin-10-yl)ethanone (0.30 g, 1.24 mmol). The reaction mixture was stirred at room temperature for 24 h, followed by dilution with ice-cold H2O and extraction with dichloromethane (3 x 20 mL). The organic layers were combined, dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography using hexane/ethyl acetate (65:35, v/v) as eluent. 2-(Methylsulfonyl)-10H-phenothiazine (product 18) was obtained as a green solid in 28% (96 mg) yield; melting point: 211-215 °C (hexane/ethyl acetate); IR (ATR diamond, cm-1 ) ν: 3351, 1567, 1310, 1297; 1H NMR (400 MHz, acetone-d6) δ: 3.22 (s, 3H, CH3), 6.90 (d, J = 9 Hz, 1H, H-9), 6.98 (d, J = 9 Hz, 1H, H-6), 7.03 (t, J = 9 Hz, 1H, H-7), 7.13 (d, J = 6 Hz, 1H, H-3), 7.20 (t, J = 9 Hz, 1H, H-8), 7.58 (s, 1H H-1), 7.66 (d, J = 6 Hz, 1H, H-4), 8.55 (bs, 1H, NH); 13C NMR (100 MHz, acetone-d6) δ: 44.2 (CH3), 114.5 (CH), 115.6 (CH), 116.9 (Cq), 118.7 (Cq), 123.8 (CH), 125.9 ( CH), 126.8 (CH), 127.8 (CH), 128.4 (CH), 134.7 (Cq), 140.9 (Cq), 147.2 (Cq).HRMS (ESI): Calculated value of C13H12NO2S2 [M + H]+: 278.0309, Measured value 278.0310.
