N([O-])=O.[Na+].N[C:6]1[C:7]([CH3:18])=[C:8]([CH:14]=[CH:15][C:16]=1[Cl:17])[C:9]([O:11][CH2:12][CH3:13])=[O:10].C(OCC)(=O)C.[BrH:25]>S(=O)(=O)(O)O.C(O)(=O)C.O.[Cu]Br>[Br:25][C:6]1[C:7]([CH3:18])=[C:8]([CH:14]=[CH:15][C:16]=1[Cl:17])[C:9]([O:11][CH2:12][CH3:13])=[O:10]A solution of sodium nitrite (13 g) in concentrated sulphuric acid was added during 0.5 hours to a solution of ethyl 3-amino-4-chloro-2-methylbenzoate (22.4 g) in acetic acid, keeping the temperature below 15° C. After stirring for a further 1 hour at 5° C., the resulting diazonium mixture was added during 0.75 hours to a solution of copper (I) bromide (31 g) in hydrobromic acid (45%, 103 ml) and water. Heating to 40° C. was continued for a further 2 hours before addition of water and extraction (ethyl acetate). The extract was washed (sodium hydroxide solution), dried (magnesium sulphate) and evaporated to give ethyl 3-bromo-4-chloro-2-methylbenzoate (22.2 g) as a brown oil, NMR (CDCl3) 1.3 (t,3H), 2.65 (s,3H), 4.3 (q,2H), 7.45 (m,2H).
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