| Hemetsberger indole synthesis | |
|---|---|
| Named after | Helfried Hemetsberger |
| Reaction type | Ring forming reaction |
The Hemetsberger indole synthesis (also called the Hemetsberger–Knittel synthesis) is a chemical reaction that thermally decomposes a 3-aryl-2-azido-propenoic ester into an indole-2-carboxylic ester.
Yields are typically above 70%. However, this is not a popular reaction, due to the lack of stability and difficulty in synthesizing the starting material.
Reaction mechanism
The mechanism is unknown. However, azirine intermediates have been isolated. The mechanism is postulated to proceed via a nitrene intermediate.
References
- Hemetsberger, H.; Knittel, D. (1972). "Synthese und Thermolyse von α-Azidoacrylestern". Monatshefte für Chemie. 103: 194–204. doi:10.1007/BF00912944. S2CID 91741917.
- Gribble, G. W. (2000). "Recent developments in indole ring synthesis-methodology and applications". J. Chem. Soc., Perkin Trans. (7): 1045–1075. doi:10.1039/a909834h.
- Gilchrist, T. L. (2001). "Activated 2H-Azirines as Dienophiles and Electrophiles" (PDF). Aldrichimica Acta. 34 (2): 51. Archived from the original (PDF) on 15 May 2013.
- Knittel, D. (1985). "Verbesserte Synthese von α-Azidozimtsäure-estern und 2H-Azirinen". Synthesis. 1985 (2): 186–188. doi:10.1055/s-1985-31149.