Synthesis of Oxazole

Synthesis of Oxazole involves methods like Robinson-Gabriel synthesis, Fischer oxazole synthesis, and cyclization of α-acylaminoketones.

1. Robinson–Gabriel Synthesis (Classical method)

   • • Reactants: α-acylaminoketones
     • Reagents: Acidic dehydrating agents (e.g., P₂O₅, POCl₃)
   • Reaction:
     • R–CO–CH₂–NH–CO–R’ → Oxazole (via cyclodehydration)
   • Mechanism:
     • Intramolecular cyclization
     • Dehydration
     • Aromatization

2. Bredereck Synthesis

   • • Reactants: α-haloketone + formamide
   • Reaction:
     • CH₃COCH₂Cl + HCONH₂ → 2-methyl-oxazole
   • Good for substituted oxazoles

3. From 1,3-dicarbonyl compounds + Hydroxylamine

   • Produces isoxazole as well, depending on structure
   • Useful in some functionalized derivatives

4. Cyclization of Acetylenic Ketones and Amides

   • Involves oxidative or Lewis acid-assisted cyclization

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