Dimethyl 2-amino-3,5-dichloroterephthalate (CAS:1258298-04-2, 200 g, 0.72 mol) was used as a starting material and dissolved in tetrahydrofuran (THF, 1 L). To this solution, isoamyl nitrite (240 mL) was slowly added at room temperature. The reaction mixture was heated to reflux and maintained for 3 hours. Upon completion of the reaction, the mixture was cooled to room temperature and subsequently concentrated under reduced pressure to remove the solvent. The resulting residue was purified by silica gel column chromatography with the eluent being a solvent mixture of petroleum ether and ethyl ether (50:1, v/v). Purification afforded the target product dimethyl 2,6-dichloroterephthalate (187 g, 98% yield) as a light yellow solid. The structure of the product was confirmed by 1H NMR (400 MHz, DMSO-d6): δ 3.86 (s, 3H), 3.92 (s, 3H), 8.00 (s, 2H).LCMS (ESI) analysis showed m/z: 263.0 [M+H]+.
