It was found that the dilithium salt (5), which was lithiated at the side-chain of 2-methyl-3-thiophenecarboxylic acid (4), was produced regioselectively by the reaction of 4 with lithium diisopropylamide (LDA). The reactions of 5 with alkyl halides resulted in the formation of 2-alkyl-3-thiophenecarboxylic acids (7). Further, δ-lactone derivatives (11) were obtained by the cyclization of the adducts (10) which were produced from 5 with aldehydes and ketones.