To a solution of o-chlorophenylacetic acid (1.04 g, 6 mmol) in methanol (25 mL) was added concentrated sulfuric acid (6 drops) and the reaction mixture was heated to reflux for 16 hours. Upon completion of the reaction, the methanol was removed by concentration under reduced pressure, and the residue was dissolved in ethyl acetate and washed with saturated aqueous sodium bicarbonate, water and saturated aqueous sodium chloride in that order. The organic layer was dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure to give o-chlorophenylacetic acid methyl ester (1.08 g, yield 97.5%) as a light yellow oil.GC-MS (EI) m/z: 184, 186 [M+].
[1] Bioorganic and Medicinal Chemistry, 2003, vol. 11, # 13, p. 2843 - 2866
[2] Tetrahedron Letters, 2003, vol. 44, # 2, p. 331 - 334
[3] Patent: WO2005/7165, 2005, A1. Location in patent: Page 43
[4] Patent: WO2005/7633, 2005, A1. Location in patent: Page 30-31
[5] Bioorganic and Medicinal Chemistry Letters, 2013, vol. 23, # 20, p. 5515 - 5518
