Synthesis
The general procedure for the synthesis of 2-thiophene glyoxalate from ethyl thiophene-2-glyoxalate was as follows: to a solution of ethyl thiophene-2-glyoxalate (4 mL, 27.17 mmol) in ethanol (60 mL) was added an aqueous 4N sodium hydroxide solution (10.2 mL, 40.76 mmol). The reaction mixture was stirred at room temperature for 18 hours. Upon completion of the reaction, the reaction solution was acidified with 2N aqueous hydrochloric acid to pH 2. Subsequently, the solvent was removed by vacuum distillation to afford 2-thiophene glyoxalic acid as a yellow solid product (quantitative yield). The resulting residue was used directly in the subsequent reaction without further purification.LCMS analysis (Method 2): [MH-] = 155 with a retention time of 0.71 min.
References
[1] Patent: WO2016/193244, 2016, A1. Location in patent: Page/Page column 80
[2] Chemical Communications, 2014, vol. 50, # 34, p. 4489 - 4491
[3] Patent: WO2016/177849, 2016, A1. Location in patent: Page/Page column 60
[4] Advanced Synthesis and Catalysis, 2018, vol. 360, # 21, p. 4184 - 4190
