Hemetsberger indole synthesis

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.[1][2]

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, aziridine[3] intermediates have been isolated. The mechanism is postulated to proceed via a nitrene intermediate.[4]

References

  1. ^ Hemetsberger, H.; Knittel, D. Monatsh. Chem. 1972, 103, 194.
  2. ^ Recent developments in indole ring synthesis-methodology and applications. Gribble, G. W. J. Chem. Soc., Perkin Trans. 1 2000, 1045-1075. (Review)
  3. ^ Gilchrist, T. L. Aldrichimica Acta 2001, 34, 51. (Review)
  4. ^ Knittel, D. Synthesis 1985, 186-188.