Phenothiazine (500 mg, 2.50 mmol) was dissolved in anhydrous toluene (5 mL) under nitrogen protection, and iodobenzene (310 mg, 2.2 mmol), sodium tert-butanolate (0.5 mL), and tris(dibenzylideneacetone)dipalladium (Pd2(dba)3, 46 mg, 0.05 mmol) were added in sequence. The reaction mixture was transferred to a sealed tube and the reaction was stirred at 160 °C for 16 hours. After completion of the reaction, it was cooled to room temperature. The organic layer was separated and the aqueous layer was extracted with dichloromethane (2 x 15 mL). The organic phases were combined, dried over anhydrous sodium sulfate (Na2SO4) and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (eluent: petroleum ether/ethyl acetate= 20:1) to afford 10-phenylphenothiazine (600 mg, 87.3%) as a white solid with a melting point of 205 °C. Nuclear magnetic resonance hydrogen spectrum (1H-NMR, 300 MHz, acetone-d6): δ 7.70 (t, J = 7.5 Hz, 2H), 7.57 (t, J = 7.2 Hz, 1H), 7.44 (d, J = 7.8 Hz, 2H), 7.06 (d, J = 7.5 Hz, 2H), 6.92 (t, J = 7.2 Hz, 2H), 6.89 (t , J = 7.2 Hz, 2H), 6.23 (d, J = 8.1 Hz, 2H). Nuclear magnetic resonance carbon spectrum (13C NMR, 100 MHz, acetone-d6): δ 144.98, 141.82, 131.64, 131.37, 129.07, 127.31, 123.37, 120.90, 116.96. The electrospray high-resolution mass spectrometry (ESI-HRMS) m/z calculated value of C18H14NS ([M + H] +) was 276.0841 and the measured value was 276.0842.
