Synthesis
General procedure for the synthesis of 3-hydroxythiophene-2-carboxylic acid from 3-benzyloxythiophene-2-carboxylic acid: a) 3-benzyloxythiophene-2-carboxylic acid (1.0 g) was hydrogenated with 10% palladium-carbon catalyst (1.8 g) in a mixture of ethanol (150 mL) and 2N hydrochloric acid (4.5 mL) for 2 hours at 45 psi hydrogen pressure. Upon completion of the reaction, the mixture was filtered through a layer of diatomaceous earth and the filtrate was concentrated under vacuum to afford 3-hydroxythiophene-2-carboxylic acid (600 mg, 98% yield) as an off-white solid product. The product was characterized by 1H NMR (300 MHz, CDCl3): δ 6.78 (d, 1H), 7.49 (d, 1H). Mass spectrometry (APCI) showed m/z=145 (M+1).LC/MS analysis showed a retention time of 1.15 min.
