Piperazine → 1,2-Dihydro-4-phenyl-8-piperazinylimidazo[1,2-a]quinoxaline 5-oxide

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Under a nitrogen atmosphere, 1,2-dihydro-8-fluoro-4-phenylimidazo[1,2-a]quinoxaline 5-oxide (40 g 0.142 mol) and piperazine (122 g, 419 mol) were heated at 9° C., for 3.5 hrs. The solvent was removed in vacuo and the resulting residue was dissolved in dichloromethane. The resulting solution was washed with water, dried over anhydrous magnesium sulphate and concentrated in vacuo to yield an orange solid. The orange solid was recrystallized from chloroform-ethyl acetate to yield 1,2-dihydro-4-phenyl-8-piperazinylimidazo[1,2-a]quinoxaline 5-oxide, (45 g) as orange crystals, m.p. 209°-211° C. (Found: C, 68.56; H,6.06; N,19.99%; C20H21N5O.O.2H2O requires C, 68.43; H,6.14; N,19.95%) represented by the structural formula: ##STR24##

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