Hydrochloric Acid → 2-Thiophenecarboxylic acid, 3-(chlorosulfonyl)-, methyl ester

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Reaction Steps

48 G. (0.196 mol) of the obtained 3-chlorosulfonylthiophene-2-carboxylic acid chloride are dissolved in 500 ml. of absolute chloroform, 9.6 g. (0.3 mol) of absolute methanol are added and the solution is heated to reflux for 3 hours [until no more hydrogen chloride evolution]. The mixture is evaporated to dryness in vacuo and the residue allowed to crystallize out. There is obtained pure 3-chlorsulfonylthiophene-2-carboxylic acid methyl ester. 2.41 G. (0.010 mol) of the obtained 3-chlorosulfonylthiophene-2-carboxylic acid methyl ester are dispersed together with 1.53 g. of sarcosine ethyl ester hydrochloride in 10 ml. of absolute pyridine and stirred at room temperature. After 2 hours, the mixture is poured on to 50 ml. of ice-cold 2-N hydrochloric acid and extracted five times with 20 ml. of methylene chloride each time. The combined organic phases are dried over sodium sulfate, filtered and evaporated. The crystalline residue is digested with a small amount of ice-cold ethanol.

Provenance & Evidence