2-Thiophenecarboxylic acid → 5-Chloromethyl-2-thienylcarboxylic acid

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Reaction Steps

2-Thiophenecarboxylic acid is treated in a solution of chloroform with chloromethyl ether in the presence of 0.9 to 2.2 equivalents of aluminum chloride to give 5-chloromethyl-2-thienylcarboxylic acid. Treatment of theobtained acid with excess thionyl chloride at room temperature for about 16hours yields the acid chloride which is reacted with diazomethane to give the corresponding diazoketone. A methanol solution of the diazoketone is irradiated under nitrogen for about one hour with a high pressure mercury lamp using a Quarz filter. The methyl 5-chloromethyl-2-thienylacetate is obtained upon work up and column chromatography on silica gel. The acetateis hydrolyzed by treatment of a 1:1 mixture of acetic acid and concentratedhydrochloric acid at room temperature overnight to give 5-chloromethyl-2-thienylacetic acid.

Provenance & Evidence