N[C:2]1[C:3]([CH3:13])=[CH:4][C:5]([Br:12])=[C:6]([CH:11]=1)[C:7]([O:9][CH3:10])=[O:8].[ClH:14].N([O-])=O.[Na+]>O1CCOCC1.O.[Cu]Cl>[Br:12][C:5]1[CH:4]=[C:3]([CH3:13])[C:2]([Cl:14])=[CH:11][C:6]=1[C:7]([O:9][CH3:10])=[O:8]To a cooled solution (15° C.) of methyl 5-amino-2-bromo-4-methylbenzoate (122 g, 0.5 mol) in 1,4-dioxane (633 mL), was added conc. hydrochloric acid (550 mL). After the mixture was cooled to 5° C., a solution of sodium nitrite (35.53 g, 0.515 mol) in 83 mL of H2O was added dropwise at such a rate that the reaction temperature was kept below 0° C. After being stirred at 0° C. for 2 h, the reaction mixture was added slowly to a flask containing copper (I) chloride (59.4 g, 0.6 mol) and conc. hydrochloric acid (275 mL). It was stirred for 40 min, at which time TLC demonstrated that the reaction was complete. The reaction mixture was poured over ice water (2 L) and then filtered. The filter cake was dissolved in EtOAc (1.5 L). The organic layer was washed with brine (3×500 mL) and then dried over anhydrous Na2SO4 Concentration under reduced pressure provided the title compound as light yellow crystals. Yield: 120 g (92.6%). 1H-NMR (CDCl3, 300 MHz): δ 7.82 (s, 1H), 7.54 (s, 1H), 3.92 (s, 3H), 2.38 (s, 3H); MS ESI (m/z) 262 (M)+, calc. 262.
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