To a solution of bis(2,4-dimethoxybenzyl)amine (12 g) and 3-chloro-4-fluorobenzene-1-sulfonyl chloride (8.66 g) in dichloromethane (120 mL) was added N,N-diisopropylethylamine (13.5 mL) and catalytic amount of 4-dimethylaminopyridine. The mixture was stirred at room temperature overnight. The mixture was diluted with ethyl acetate (600 mL) and washed with 5% aqueous HCl, water and brine. After drying over Na2SO4, the mixture was filtered and the filtrate was concentrated under vacuum to give crude product which was loaded on a 400 g silica gel column and eluted with 30% ethyl acetate in hexane to give the title compound.
