Pellizzari reaction

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The Pellizzari reaction was discovered in 1911 by Guido Pellizzari, and is the

1,2,4-triazole.[1]

The product is similar to that of the

Einhorn-Brunner reaction, but the mechanism itself is not regioselective
.

An overview of the Pellizzari reaction
An overview of the Pellizzari reaction

Mechanism

The mechanism begins by the nitrogen in the hydrazide attacking the

carbonyl carbon on the amide to form compound 3. The negatively charged oxygen then abstracts two hydrogens from neighboring nitrogens in order for a molecule of water to be released to form compound 5. The nitrogen then performs an intramolecular attack on the carbonyl group to form the five-membered ring of compound 6. After another proton migration from the nitrogens to the oxygen, another water molecule is released to form the 1,2,4-triazole 8.[2]

Pellizzari reaction mechanism
Pellizzari reaction mechanism

Uses

The synthesis of the 1,2,4-triazole has a wide range of biological functions.[

hypoglycemic properties. 3-benzylsulfanyl derivates of the triazole also show slight to moderate antimycobacterial activity, but are considered moderately toxic. [3]

Problems and variations

The Pellizzari reaction is limited in the number of substituents that can be on the ring, so other methods have been developed to incorporate three elements of diversity. Liquid-phase synthesis of 3-alkylamino-4,5-disubstituted-1,2,4-triazoles by PEG support has given moderate yields with excellent purity.[4] In practice, the Pellizzari reaction requires high temperatures, long reaction times, and has an overall low yield. However, adding microwave irradiation shortens the reaction time and increases its yield.[5]

Related reactions

  • Einhorn-Brunner reaction

References

  1. Gazz. Chim. Ital.
     1911, 41, 20.
  2. ISBN 9780471704508
    .
  3. PMID 15081345
    .
  4. doi:10.1016/j.tetlet.2005.05.121
    .
  5. doi:10.1016/j.tet.2012.01.003. Archived from the original
    (PDF) on 2016-03-04. Retrieved 2014-05-20.
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