Ethyl 2-chlorooxazole-4-carboxylate

Substituted oxazolo[4,5-Z ]pyridines 138 (and quinolines) were synthesised in high yields from zwitterion or hydroxyamidine derivatives 137, obtained by treatment of non-enolisable amides 136 with the complex base NaNH2-/-BuONa, via hetaryne intermediates. Intramolecular cyclization and NH3 elimination to give 138 were performed in dimethylacetamide by heating or microwave irradiation <03S2033>. Different approaches to oxazolo[4,5-c]quinoline-4(5/f)-ones from ethyl 2-chlorooxazole-4-carboxylate have also been described <03OL2911>. 

The readily available ethyl 2-chlorooxazole-4-carboxylate proved to be a versatile scaffold for the synthesis of 2,4-disubstituted oxazoles and 2,4,5-trisubstituted oxazoles. 

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