A solution of methanesulfonyl chloride (0.33 g, 0.003 mol) in dichloromethane (20 ml) was cooled in an ice-bath. To this solution was added dropwise with stirring, a solution of triethylamine (0.29 g, 0.003 mol) and 1,2-dihydro-4-phenyl-8-piperazinylimidazo[1,2-a]quinoxaline 5-oxide (1 g, 0.003 mol) in dichloromethane (10 ml). The reaction mixture was stirred for an additional 15 minutes and then was allowed to warm to room temperature. The reaction mixture was washed with water, dried over anhydrous magnesium sulphate and then evaporated to dryness under reduced pressure to yield a yellow solid. Recrystallization from ethyl acetate yielded 1,2-dihydro-8-(4-(methylsulphonyl)piperazinyl)-4-phenylimidazo[1,2-a]quinoxaline 5-oxide (0.8 g), as yellow crystals, m.p. 252°-253° C. (Found: C,59.19; H,5.35; N,16.33%; C21H23N5O3S requires C,59.29; H,5.41; N,16.47%) having the formula: ##STR31##
