Synthesis
Concentrated sulfuric acid (15 mL) was slowly added to a stirring solution of 5-chlorothiophene-2-carboxylic acid (15 g, 0.0925 mol) in ethanol (300 mL) at room temperature. The reaction mixture was stirred continuously under anhydrous conditions for 16 hours. Upon completion of the reaction, the reaction mixture was concentrated by distillation under reduced pressure. The concentrate was diluted with ethyl acetate (300 mL) and the organic layer was subsequently washed sequentially with water (3 x 100 mL), saturated sodium bicarbonate solution (3 x 100 mL) and saturated saline (100 mL). The organic layer was dried over anhydrous sodium sulfate and concentrated under reduced pressure to give ethyl 5-chlorothiophene-2-carboxylate (14 g, 80% yield) as a colorless liquid.
References
[1] Patent: WO2015/18534, 2015, A1. Location in patent: Page/Page column 39
[2] Journal of the American Chemical Society, 1954, vol. 76, p. 5131
[3] Chemistry - A European Journal, 2016, vol. 22, # 1, p. 211 - 221
