A. 2-Chloro-6-methylbenzoic acid (7.82 g, 45.8 mmol) was suspended in thionyl chloride (20.0 mL, 275 mmol) and refluxed in an oil bath at 85 °C for 16 hours. After the reaction was completed, the resulting light brown solution was concentrated under reduced pressure to obtain 2-chloro-6-methylbenzoyl chloride as a light brown oil, which could be used in the next reaction without further purification. The above prepared chloroyl chloride (45.8 mmol) was dissolved in dichloromethane (20 mL) and cooled in an ice bath. Methanol (10 mL, 247 mmol) was added slowly and the ice bath was subsequently removed. After 45 minutes of reaction, HPLC analysis showed that the ratio of starting acid to product ester was 4:1. Subsequently, triethylamine (15 mL, 108 mmol) was added dropwise over a few minutes, which was exothermic and accompanied by smoke generation. After stirring at room temperature overnight, HPLC confirmed the complete conversion of the reaction to the target product. The reaction mixture was poured into a mixture of ether (200 mL) and saturated aqueous sodium bicarbonate (100 mL) and partitioned. The aqueous layer was extracted with ether (3 x 50 mL), the organic layers were combined, washed with brine, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure to give a yellow oil. Purification by fast chromatography with 0-10% ethyl acetate/hexane gradient elution gave methyl 2-chloro-6-methylbenzoate (7.38 g, 87% yield) as a clear colorless liquid.1H-NMR (400 MHz, CDCl3) δ: 7.24-7.19 (2H, m), 7.14-7.08 (1H, m), 3.95 (3H, s) , 2.32 (3H, s) ppm.
