S(S([O-])=O)([O-])=O.[Na+].[Na+].[N+:9]([C:12]1[C:17](=[O:18])[C:16]2[CH:19]=[C:20]([Cl:23])[CH:21]=[CH:22][C:15]=2[O:14][CH:13]=1)([O-])=O>O.C(O)C>[NH2:9][C:12]1[C:17](=[O:18])[C:16]2[CH:19]=[C:20]([Cl:23])[CH:21]=[CH:22][C:15]=2[O:14][CH:13]=1Sodium dithionite (20 g, 0.115 mole) was added to a suspension of 3-nitro-6-chloro-4H-1-benzopyran-4-one (7.0 g, 0.037 mole) in water (80 ml) and absolute ethanol (30 ml). The reaction mixture was refluxed under nitrogen for 3 hrs., concentrated at reduced pressure and filtered. The solids were washed with water and recrystallized from acetone to give yellow crystals (5.44 g, 90%), m.p. 184°-186°.
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