Synthesis of Pyrazole

Synthesis of Pyrazole involves methods like Knorr synthesis using 1,3-dicarbonyl compounds and hydrazines.

1. Condensation of 1,3-Dicarbonyl Compounds with Hydrazine (most common method)

   • Reactants:

     • 1,3-diketones (e.g., acetylacetone)
     • Hydrazine (NH₂NH₂) or substituted hydrazines

   • Reaction:

     • CH₃COCH₂COCH₃  +  NH₂NH₂  →  3,5-Dimethylpyrazole  +  H₂O
   • 

   • Mechanism:

     • Formation of hydrazone at one carbonyl
     • Intramolecular cyclization
     • Elimination of water → Pyrazole ring

   • Advantages:

     • Simple, high-yielding, allows substitution at 3 and 5 positions

2. Knorr Pyrazole Synthesis

   • Reactants: α-hydrazino ketones + β-ketoesters
   • Use: For substituted pyrazoles with varying groups at C-3 and C-5

3. From α,β-unsaturated ketones and hydrazines

   • Hydrazine adds to the double bond and then cyclizes.

Thank you for reading from Firsthope's notes, don't forget to check YouTube videos!