General procedure for the synthesis of o-(trifluoromethyl)benzenesulfonamide from 2-(trifluoromethyl)benzenesulfonyl chloride:
Intermediate 1: Preparation of 2-(trifluoromethyl)benzenesulfonamide (see Scheme 3, compound XXI)
To a solution of 2-(trifluoromethyl)benzenesulfonyl chloride (5 g, 20.44 mmol, 1.00 eq.) in anhydrous THF (5.00 mL) was slowly added an ethanol solution of 2 M ammonia (71 mL) under nitrogen protection and at room temperature. The reaction mixture was stirred at room temperature for 20 hours. After completion of the reaction, the solvent was removed by evaporation and the residue was redissolved in EtOAc (150 mL) and washed sequentially with saturated aqueous NH4Cl solution (50 mL) and brine (50 mL). The organic layer was dried over anhydrous MgSO4, filtered and the solvent concentrated to give pure 2-(trifluoromethyl)benzenesulfonamide as a pale yellow solid (4.6 g, 89% yield, 98.6% HPLC purity). The compound was used directly in the next reaction without further purification.
1H NMR (300MHz, CDCl3) δ: 5.0 (m, 2H), 7.6 (m, 2H), 7.8 (m, 1H), 8.3 (m, 1H).
MS (ESI): m/z 224.1 [M-H]-.
