Stannous chloride dihydrate → 5-Amino-7-bromo-6-chloro-1,4-dihydro-2,3-quinoxalinedione

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A suspension of 7-bromo-6-chloro-5-nitro-1,4-dihydro-2,3-quinoxalinedione (50 mg, 0.16 mmol) and tin (II) chloride dihydrate (176 mg, 0.780 mmol, Aldrich, used as received) in ethanol (5 mL) was refluxed for 7 h. It was then cooled to r.t. and poured into ice (10 g). The suspension was then basified with 10% aq. NaHCO3 (25 mL) to pH 8-8.5 (pH paper) and extracted with ethyl acetate (50 mL). The ethyl acetate extract was washed with water and brine, dried over Na2SO4 and evaporated to give a solid which was dried under high vacuum to furnish 28 mg (62%) of pure title compound as a brown powder, m.p. >350° C.; 1H NMR (DMSO-d6) δ 5.888 (br s, 2H), 6.075 (s, 1H), 11.286 (s, 1H), 11.827 (s, 1H).

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