Thiophene-2-carboxylic acid is an organic compound with the formula SC4H3CO2H.

[1] Copper(I) thiophene-2-carboxylate is a catalyst for Ullmann coupling reactions.

It can be prepared by the oxidation of thiophene-2-carboxaldehyde or, more practically, 2-acetylthiophene.

[2] Upon treatment with LDA, thiophene-2-carboxylic acid undergoes double deprotonation to give the 5-lithio derivative, a precursor to many 5-substituted derivatives.

[3] Thiophene-2-carboxylic acid has been widely studied as a substrate in coupling reactions and olefinations.