2-Aminothiophenol → 2-phenyl-4H-1,4-benzothiazin-3-one

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2-Phenyl-3,4-dihydro-2H-1,4-benzothiazine: To bromo-phenyl-acetic acid methyl ester (4.88 g, 21 mmol) in DMF (15 mL) under an argon atmosphere was added 2-amino-benzenethiol (2.3 mL, 21 mmol) and the reaction was stirred at rt overnight. The reaction mixture was diluted with EtOAc (5 mL) and water (50 mL) and the crude product was collected by filtration, washed with warm EtOAc, and dried to give 2-phenyl-4H-1,4-benzothiazin-3-one as a white solid (3.49 g). LC/MS m/z 242 (M+H)+. To this intermediate (3.48 g, 14.4 mmol) in THF (50 mL) under an argon atmosphere was added 1M BH3.THF (50 mL, 50 mmol) and the reaction was stirred at rt overnight. The reaction was quenched with 1N HCl and extracted with ether. The combined organic fractions were dried over MgSO4 and concentrated. 201A was purified by recrystallization from hot EtOAc/hexanes to yield pale pink crystals (1.5 g). LC/MS m/z 228.2 (M+H)+.

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