Studies with 2-arylhydrazono-3-oxopropanals: Routes for the synthesis of pyridazine-3,4-dicarboxylate and 3,5-diaroyl pyrazoles

Abstract

The title compounds 3a-j were synthesized via coupling of enaminones 2a-d with aromatic diazonium salts. The reaction of 3b-f,h-j with dimethyl acetylenedicarboxylate and triphenylphosphine afforded dimethyl 2-aryl-6-aroyl-2,3-dihydropyridazine-3,4-dicarboxylates 7b-f,h-j. . The reaction of 3b,d,f,g with phenacyl bromide afforded 3-aroyl-5-benzoylpyrazoles 9b,d,f,g.,while compound 3i condensed with benzoylacetonitrile to yield pyridazin-6-imine 11.Reaction of 3c-e,h,j with p-toluidine yielded the enamineazo 12c-e,h,j. The structures of 7b,d,i and 9b were confirmed by X-ray crystal structure determination.

Tandem one-pot synthesis of 2-arylcinnolin-6-one derivatives from arylhydrazonopropanals and acetoacetanilides using sustainable ultrasound and microwave platforms

“… 52,53 Then, initial attempts to perform the annulation of the 3-oxo-2-phenylhydrazonopropanal 1a with acetoacetanilide 2 in ethanol in the presence of triethylamine were conducted under conventional thermal heating. The expected pyridazine 4 or phenylazophenol 6 structures, according to the previously published protocols 54,55 could not be detected, however the assigned product was established as 2-arylcinnolin-6(2 H )-one derivative 3a ( Scheme 1 ). To our delight, phenylhydrazonopropanal 1a satisfactorily reacted with double equivalent of acetoacetanilide 2 to give the aldol-condensation followed by Michael-type addition product 3a, through in situ elimination of three molecules of water during the reaction path ( Scheme 1 ).…”

Bis-enaminones as precursors for synthesis of novel 3,4-bis(heteroaryl)pyrazoles and 3,6-bis-(heteroaryl)-pyrazolo[3,4-d]pyridazines

“…Enaminones of type I have been reported to couple with arenediazonium salts to give the respective hydrazones II (Scheme 1). [1][2][3][4] In conjunction with our recent work on bisenaminones of type III, [5][6][7][8][9][10] we decided to study their azo coupling with diazotised aromatic and heterocyclic amines and to explore the reactions of the resulting azo-coupled products IV and V with hydrazine hydrate. Our aim was to shed some light on the site selectivity in the latter reactions and explore their utility to synthesise new ter-heterocycles of type VI and VII (Fig.…”