Hydrogenation of thiophens via the consecutive electron and proton transfer to thiophenium ions

Abstract

Thiophen and 2-ethylthiophen are hydrogenated to the corresponding 2,5-dihydrothiophens with Zn and CF₃CO₂H via a mechanism involving the protonation of the thiophen ring to the respective thiophenium ion, followed by the transfer of two electrons from Zn and the second proton from the acid.