Reaction Steps
To a solution of 3,3-dimethyl-2,3-dihydro-benzofuran (160 mg, 1.08 mmol) in dichloromethane (2 mL) at −10° C. was added chlorosulfonic acid (72 μL, 1.08 mmol). The mixture was stirred at −10° C. for 15 minutes, then the solvent was evaporated to give 3,3-dimethyl-2,3-dihydro-benzofuran-5-sulfonic acid [1H-NMR (300 MHz, CDCl3): 1.37 (s, 6H), 4.35 (s, 2H), 6.85 (d, J=8.2 Hz, 1H), 7.67 (d, J=2.1 Hz, 1H), 7.73 (dd, J1=8.5 Hz, J2=2.1 Hz, 1H), 10.12 (br s, 1H)]. The residue was diluted with thionyl chloride (1 mL, 13.71 mmol) and one drop of dimethylformamide was added. After 45 minutes reflux and evaporation of the solvent, the solid compound was washed in a mixture of dichloromethane/hexane to give 3,3-dimethyl-2,3-dihydro-benzofuran-5-sulfonyl chloride [1H-NMR (300 MHz, CDCl3): 1.41 (s, 6H), 4.41 (s, 2H), 6.92 (d, J=8.8 Hz, 1H), 7.74 (d, J=2.3 Hz, 1H), 7.87 (dd, J1=8.5 Hz, J2=2.1 Hz, 1H)]. A solution of methylamine 2.0 M in tetrahydrofuran (0.81 mL, 1.62 mmol) was then slowly added and the mixture was stirred at room temperature for 15 minutes. The solvent was evaporated to afford 215 mg of 3,3-dimethyl-2,3-dihydro-benzofuran-5-sulfonic acid methylamide. 83% yield. 1H-NMR (300 MHz, CDCl3): 1.38 (s, 6H), 2.66 (d, J=5.3 Hz, 3H), 4.21 (m, 1H), 4.34 (s, 2H), 6.86 (d, J=8.5 Hz, 1H), 7.60 (d, J=2.1 Hz, 1H), 7.66 (dd, J1=8.5 Hz, J2=1.8 Hz, 1H).
