Synthesis
Step 2: Synthesis of 5-chloro-1-methyl-1H-indole-2-carboxylic acid (43.2)
To a THF solution (10 mL) of methyl 5-chloro-1-methyl-1H-indole-2-carboxylate (43.1, 224 mg) was added an aqueous solution (2 mL) of LiOH (36 mg, 1.5 mmol). The reaction mixture was stirred at room temperature for 2 hours. Upon completion of the reaction, the solvent was removed under reduced pressure and the residue was dissolved in 1N aqueous hydrochloric acid solution (10 mL). The resulting suspension was allowed to stand for 10 minutes, then filtered through filter paper, collected as a solid and dried under vacuum to afford 163 mg (77.6% yield) of 5-chloro-1-methyl-1H-indole-2-carboxylic acid (43.2) as a beige powder.
References
[1] Patent: KR101725451, 2017, B1. Location in patent: Paragraph 0294; 0301-0303
[2] Patent: WO2016/40449, 2016, A1. Location in patent: Paragraph 00508-00509
[3] Patent: WO2006/66879, 2006, A2. Location in patent: Page/Page column 53; 48
[4] Bioorganic and Medicinal Chemistry, 2018, vol. 26, # 21, p. 5664 - 5671
