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