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The general procedure for the synthesis of 2-bromo-5-cyanobenzoic acid from 2-amino-5-cyanobenzoic acid was as follows: tert-butyl nitrite (1.15 ml, 8.63 mmol) was added dropwise over 2 min at 0 °C to a suspension of copper (II) bromide (1.6 g, 7.1 mmol) in acetonitrile (30 ml). Subsequently, 2-amino-5-cyanobenzoic acid (1.0 g, 6.17 mmol) was added in batches over 10 min at 0 °C. The reaction mixture was stirred at 0 °C for 2 h, then brought to room temperature and stirred overnight. After completion of the reaction, half of the solvent was evaporated under reduced pressure. The residue was dissolved in a mixture of 1N HCl (15 ml) and ethyl acetate (30 ml). The organic layer was extracted with 1N NaOH (3 x 10 ml). The aqueous layer was acidified with 2N HCl and a solid was precipitated. The solid was collected by filtration, washed with water and dried under high vacuum at 50°C to give 2-bromo-5-cyanobenzoic acid (0.92 g, 66% yield) as a yellow solid.

[1] Patent: WO2005/23260, 2005, A1. Location in patent: Page/Page column 48
[2] Patent: US2005/209241, 2005, A1. Location in patent: Page/Page column 20