Step a: Synthesis of methyl 2,6-dichloro-4-cyanobenzoate
Methyl 4-carbamoyl-2,6-dichlorobenzoate (100 mg, 0.4 mmol) was dissolved in pyridine (2 mL) and trifluoroacetic anhydride (0.11 mL, 0.8 mmol) was added slowly and dropwise at 0 °C. The reaction mixture was gradually warmed to room temperature and stirred continuously for 1 hour. Upon completion of the reaction, the mixture was poured into pre-cooled ice water, the precipitated solid was filtered, washed thoroughly with cold water and dried to afford methyl 2,6-dichloro-4-cyanobenzoate (55 mg, 88% yield) as an off-white solid.
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[2] Patent: US2014/155398, 2014, A1. Location in patent: Paragraph 0468
[3] Patent: US2010/317643, 2010, A1. Location in patent: Page/Page column 101
[4] Journal of Medicinal Chemistry, 2013, vol. 56, # 11, p. 4521 - 4536