N([O-])=[O:2].[Na+].N[C:6]1[CH:11]=[CH:10][C:9]([C:12]2[O:16][C:15]([CH3:17])=[C:14]([C:18]([O:20][CH2:21][CH3:22])=[O:19])[CH:13]=2)=[CH:8][CH:7]=1>O.OS(O)(=O)=O>[OH:2][C:6]1[CH:11]=[CH:10][C:9]([C:12]2[O:16][C:15]([CH3:17])=[C:14]([C:18]([O:20][CH2:21][CH3:22])=[O:19])[CH:13]=2)=[CH:8][CH:7]=1A solution of NaNO2 (111 mg, 1.61 mmol) in water (1 mL) was added over 5 min to an ice-cold suspension of ethyl 5-(4-aminophenyl)-2-methyl-3-furanecarboxylate (395 mg, 1.61 mmol) in aqueous 1 M H2SO4 solution (12 mL). The reaction mixture was stirred at 0° C. for 20 min then was heated to 90° C. for 1 h. The cooled mixture was extracted with EtOAc. The organic layer was washed with water (2×) and brine, dried (MgSO4), filtered and concentrated under reduced pressure to yield the title compound (78 mg, 20% yield) as a white solid.
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