1.3. Five membered heterocycles with Two heteroatoms: a. Imidazole: Synthetic methods including synthesis from imidazolines, α-haloketones, Radiszewskii reaction. b. Oxazole: reaction between acid amides and α-halogenoketones eg. Acetamide and bromoacetone form 2,4-dimethyloxazole, Robinson–Gabriel synthesis by dehydration of 2-acylaminoketones, Reaction with Tosylmethyl isocyanide and aldehydes (The Van Leusen reaction) c. Thiazole: preparation α-chlorocarbonyl compound and thioacid amide– Hantzsch synthesis, Gabriel synthesis by reaction of a-Acylamino Ketones with Phosphorus Pentasulfide, Cook-Heilborn’s synthesis from a-Aminonitriles, Reactions of Imidazole, Thiazole, Oxazole with acids, Electrophilic Aromatic Substitution (EAS), nucleophilic aromatic substitution (NAS), oxidizing and reducing agents Imidazole, Oxazole & Thiazole
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