Synthesis
The general procedure for the synthesis of methyl 2,2'-dichlorophenylacetate from o-chloromandelic acid is as follows: 93.3 g (0.5 mol) of pure methyl 1-chloro-(2-chlorophenyl)acetate was mixed with 208 g (1 mol) of phosphorus pentachloride and gradually heated. The reaction was initiated at 60 °C and then warmed up to 100 °C. The heating was continued between 120°C and 130°C for 2 hours. After the release of hydrogen chloride gas ceased, the mixture was cooled to room temperature, followed by pumped decompression distillation and absorption with 200 ml of methanol. The resulting mixture was refluxed for 2 hours. The reaction mixture was concentrated using a rotary evaporator followed by treatment with dichloromethane and water. After performing phase separation, the organic phase was dried with anhydrous magnesium sulfate and dichloromethane was removed using a rotary evaporator to give 121 g of crude ester. Distillation was carried out between 80°C and 90°C at a pressure of 0.15 mmHg (19.95 Pa). Eventually 54.8 g of methyl 1-chloro-(2-chlorophenyl)acetate was obtained with 90% purity and 45% yield as determined by HPLC.
References
[1] Patent: US5132435, 1992, A
[2] Angewandte Chemie - International Edition, 2016, vol. 55, # 34, p. 10145 - 10149
[3] Angew. Chem., 2016, vol. 128, # 34, p. 10300 - 10304,5
