An efficient, green, and facile four-component reaction for the preparation of pyrano [2,3-c]pyrazole derivatives through the condensation reaction of aryl aldehydes, ethyl acetoacetate, malononitrile, and hydrazine hydrate or phenyl hydrazine in the presence of commercially available organocatalyst sodium benzoate under aqueous condition is reported. The products are produced with high yields and in shorter reaction times. It also is mild, safe, green and environmental friendly.
Several N-acyl-2-benzoylaziridines were prepared conveniently in good to high yields (71-93%) and used in the preparation of 5-benzoyloxazolines (76-91%) by a regio-and stereo-controlled reaction in the presence of NaI as an efficient catalyst under microwave irradiation in short reaction times (5-10 mins). The structure of the regioisomeric product was confirmed by X-ray analysis.
A novel procedure for the direct synthesis of 2,5-diaryloxazoles starting from N-H ketoaziridines is described. The method proceeds via the in situ formation of N-bromoketoaziridines in the presence of N-bromosuccinimide followed by the generation of intermediate azomethine ylides. A plausible mechanism for this transformation is proposed.
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