Thiophene chemistry—XII

Abstract

3-Acetyl-2-hydroxythiophene and 3-carbethoxy-2-hydroxythiophene have been prepared by acid-catalysed dealkylation of the corresponding t-butyl ethers at 160°. The t-butyl ethers were prepared via organometallic reagents derived from 3-bromo-2-t-butoxythiophene by metal-halogen interconversion with n-butyllithium at −70°. Investigations by NMR and IR spectroscopy show that these 2-hydroxythiophenes exist in the tautomeric hydroxy form in the pure liquid state and in solution. Evidence for the presence of the tautomeric α,β-unsaturated γ-thiolactone form in minute quantities is obtained from the formation of a dimer in the case of 3-carbethoxy-2-hydroxythiophene.