Gewald reaction
From Wikipedia, the free encyclopedia
| Gewald reaction | |
|---|---|
| Named after | Karl Gewald |
| Reaction type | Ring forming reaction |
| Identifiers | |
| Organic Chemistry Portal | gewald-reaction |
The Gewald reaction (or the Gewald aminothiophene synthesis) is an organic reaction involving the condensation of a ketone (or aldehyde when R2 = H) with a α-cyanoester in the presence of elemental sulfur and base to give a poly-substituted 2-amino-thiophene.[1][2]
The reaction is named after the German chemist Karl Gewald.[3][4][5]
The reaction mechanism of the Gewald reaction was elucidated 30 years after the reaction was discovered.[6] The first step is a Knoevenagel condensation between the ketone (1) and the α-cyanoester (2) to produce the stable intermediate 3. The mechanism of the addition of the elemental sulfur is unknown. It is postulated to proceed through intermediate 4. Cyclization and tautomerization will produce the desired product (6).
Microwave irradiation has been shown beneficial to reaction yields and times.[7]
