Thiophene-2a-methylacetic acid

A mixture of 10.3 g of thiophene-2a-methylacetic acid [prepared by process of Bercot-Vatteroni, et al., Bull. Soc. Chim. (1961) pp. 1820-21], 11.10 g of benzoyl chloride and a suspension of 23.73 g of aluminum chloride in 110 cc of chloroform was allowed to stand for 15 minutes and was then poured into a mixture of ice and hydrochloric acid. The chloroform phase was extracted with a 10% aqueous potassium carbonate solution and the aqueous alkaline phase was acidified with N hydrochloric acid and was then extracted with ether. The ether was evaporated off and the residue was crystallized from carbon tetrachloride to obtain a 54% yield of 5-benzoyl-thiophene-2a-methylacetic acid melting at 83°C to 85°C. The product occurred in the form of colorless crystals soluble in dilute alkaline solutions, alcohol and ether and insoluble in water. 

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