Synthesis of Nitrogeneous Compounds from 6-Unsaturated 1, 3-Dicarbonyl Esters. Part I. Substituted Pyrazoles, Isoxazoles and Oxyquinoxalines

Abstract

Condensation of 4-substituted-but-3-en-2-ones (1) with ethyl oxalate gave ethyl 6-aryl-2,4-dioxo-A2-hexenoates (2) and were interconverted to the methyl esters by alcoholysis. Compounds (2) were converted by hydrazine or arylhydrazine into the corresponding ethyl 1-H/aryl-5-substituted-pyrazole¬3-carboxylates (3), which were hydrolysed to the acids (4). With hydroxyl-amine, the ethyl hexenoates (2) afforded 3,5- disubstituted-isoxazoles (5), whereas, with o-phenylenediamine they gave oxyquinoxaline derivatives (6). The 1,3-diketo-esters (2) on reaction with acylhydrazines gave the acylhydrazones (7) which were cyclized to the corresponding N-acylpyrazoles (8). Reaction of (1) with arylhydrazines afforded the corresponding hydra-zones (9) which on boiling with ethanol containing two drops of HC1 underwent cyclization to the pyrazolines (10). Oxidation of (10) with an excess of bromine-water produced the brominated pyrazole derivatives (11). Furthermore, the condensation of the a,(3-unsaturated ketones (1) with acylhydrazines furnished the corresponding hydrazones (12).