tetrabutylammonium hydroxide (0.28 g of 40% aqueous solution) was added to a solution of 2,3-dichloro-N-(5,6-dichloro-3-methoxy-2-pyrazinyl)-N-{[2-(trimethylsilyl)ethoxy]methyl}benzenesulfonamide (0.25 g) in 1,2-dimethoxyethane (3.0 mL) at room temperature. After 16 h, the solution was diluted with ethyl acetate (20 mL). The organic solution was washed with aqueous citric acid (10 mL) and brine, dried (MgSO4) and evaporated. Chromatography on silica gel eluting with ethyl acetate/isohexane mixtures gave the title compound containing the SEM group, as a white solid (0.08 g). The solid was dissolved in trifluroacetic acid (2.0 mL) and dichloromethane (2.0 mL) and stirred at room temperature for 1 h. The reaction mixture was concentrated and chromatography on silica gel eluting with ethyl acetate/isohexane mixtures gave the title compound as a white solid (0.027 g).
