2‐Arylhydrazono‐3‐oxopropanals in Heterocyclic Synthesis: Synthesis of Arylazopyrazole, Arylazoisoxazole and Dialkylpyridazine‐5,6‐dicarboxylate Derivatives. New One‐Step Synthesis of Arylazopyrimidines.

Abstract

A novel synthesis of arylpyrazole, isoxazole, dialkyl 1,6-dihydropyridazine 5,6-dicarboxylate derivatives and a new one-step synthesis of azolopyrimidines under microwave-assisted conditions are reported.

Synthesis and tautomerism of aryl- and hetaryl-azo derivatives of bi- and tri-heterocycles

“…Similarly, condensation of 2-aminobenzimidazole 208 with each of ethyl 2-arylhydrazono-3-oxo-butanoate 126A basis of NOE difference that revealed that the ethyl group and benzimidazole-H are spatially proximal (Scheme 80A) [60].…”

“…Treatment of the latter with arylhydrazonomalononitrile afforded the corresponding 2,5,7-triamino-3,6-bis-arylazopyrazolo[1,5-a]pyrimidines 127 (Scheme 41) [55,59,60].…”

“…[50] and 2-arylhydrazono-3-oxopentanal 126B[60] in refluxing ethanol afforded the respective 3-arylazo derivative of pyrimido[1,2-a]benzimidazole 234A and 234B. The isomeric structure of the latter, namely 234C, was discarded on the…”

β-Enamino Esters in Heterocyclic Synthesis: Synthesis of Pyrazolone and Pyridinone Derivatives

“…As part of our ongoing studies on the synthesis of nitrogen-containing compounds and in conjunction of our interest in the chemistry of enamines [ 20 , 21 , 22 , 23 , 24 , 25 ], we report herein the synthesis of the starting enamino esters 2 and 3 and a study of their reactivity towards some selected nitrogen and carbon nucleophiles as well as benzenediazonium salts to synthesize the new pyrazolone, pyridinone and phenylhydrazone derivatives with the expectation that they would be of biological interest. In our chemical reactivity studies described here, we principally employed the intermediates 2b and 3 due to their easy preparation and good yield of the subsequent reactions.…”

Synthesis with Nitriles: Synthesis of Some New Mercaptopyridazine, Mercaptopyridazino[1,6-a]quinazoline and Thiophene Derivatives

“…Continuing our interest in synthesis of pyridazines [ 12 , 13 , 14 ], some new functionally substituted pyridazine and pyridazinoquinazoline derivatives were required. 2-(1-(4-Bromophenyl)-2-thiocyanato-ethylidene)malononitrile ( 3 ) seemed a good candidate to fulfil this objective via its coupling with the diazotized aromatic amines 4a - d to afford the arylhydrazone derivatives 5a - d , followed by cyclization to the pyridazines 6a - d ( Scheme 1 ), by analogy with previously reported work on related systems [ 15 , 16 ].…”