Substituted Hydrazonals as Building Blocks in Heterocyclic Synthesis: A New Route to Arylhydrazonocinnolines

Abstract

2-heteroylhydrazonopropanals 2a-e and 3-oxo-2-arylhydrazonopropanals 2f-k were prepared via coupling of enaminones 1 with aromatic diazonium salts. Compounds 2a-c condensed with hydrazine hydrate to yield the corresponding hydrazones 3a-c which afford on cyclisation the cinnoline derivatives 6a-c, while condensation of 2g, j with hydrazine hydrate directly yielded the pyrazole derivatives 4g-j. Condensation of 2a-c, f, g with phenyl hydrazine gave the corresponding phenyl hydrazone derivatives 7a-c, f, g. Structures of 2a, h and 3a were assessed by single crystal X-ray analyses.

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

“…Coupling enaminones 2 with aromatic diazonium salts afforded the products 3a-j which were previously shown to exist, in the solid state, in the anti form according to the X-ray crystal structure determination of 3a,h published recently by our group. 8 This agrees with a recent observation 9 that in the 2-arylhydrazonoketones stereoelectronic factors overweigh any possible lock of conformation that may occur due to hydrogen bonding. (Scheme 1).…”

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

“…At rst, 3-oxo-2-arylhydrazonopropanal derivatives 1a-o were synthesized using reported procedure in the literature. 52,53 Then, initial attempts to perform the annulation of the 3-oxo-2phenylhydrazonopropanal 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(2H)-one derivative 3a (Scheme 1).…”

Recent developments in chemical reactivity of N,N-dimethylenamino ketones as synthons for various heterocycles

“…24,25 The structure and chemistry of these b-ketoaldehydes has attracted much attention with plenty of uses for these compounds, in heterocyclic synthesis, being reported recently. [26][27][28][29][30][31] It has been noted that in DMSO these molecules exist as a mixture of two conformers E and Z. 22,27,28 Coupling 21,22,[32][33][34] of diazotized aromatic amines with the aminovinyl ketones 1d,f,g,h and 1q resulted in products of coupling and hydrolysis of the dimethylamine moiety.…”