Gewald reaction

The reaction mechanism of the Gewald reaction has only recently been elucidated.

The Hantzsch pyridine synthesis, the Gewald reaction and the Feist-Benary furan synthesis all contain a Knoevenagel reaction step.

Specialized thiophenes can be synthesized similarly using or Lawesson's reagent as the sulfiding agent, via the Gewald reaction, which involves the condensation of two esters in the presence of elemental sulfur.

In related chemistry, malononitrile is a suitable starting material for the Gewald reaction, where the nitrile condenses with a ketone or aldehyde in the presence of elemental sulfur and a base to produce a 2-amino thiophene.