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

Abstract

Coupling of bis-enaminones with benzenediazonium chloride and 3-diazo-1,2,4-triazole proved to be convenient routes for the synthesis of novel 3,4-bis(pyrazol-3-yl)pyrazoles and 3,6-bis(heteroaryl)pyrazolo[3,4-d]pyridazines which have not been reported previously. The structures of the products were elucidated on the basis of their spectral properties, elemental analyses and, wherever possible, by alternate synthesis.

Bis-enaminones as versatile precursors for terheterocycles:synthesis and reactions

“…The assigned structure 145 was confirmed by comparison of 145 with an authentic sample of 146, prepared by alternate unambiguous synthesis as depicted below. 33 …”

Convenient Synthesis and Biological Activity of 4-minomethylene 1-phenylpyrazolidine-3,5-diones

“…Enaminone 1 was treated with some 1,4-binucleophiles such as o-aminophenol and o-aminothiophenol. Thus, treatment with o-aminophenol, in boiling glacial acetic acid, gave (4E)-4-(((2-hydroxyphenyl)amino)methylidene)-1-phenylpyrazolidine-3,5-dione (2). Similarly, when o-aminothiophenol was reacted with 1, in boiling dioxane, led to (4E)-4-(((2-mercaptophenyl)amino)methylene)-1-phenylpyrazolidine-3,5-dione (3).…”

“…It is known that, β-enaminone derivatives are push-pull electron systems which represent versatile synthetic intermediates. These category of compounds showed significant reactivity in a wide variety of nucleophilic and electrophilic substitution [1,2], photochemical [3], reduction and oxidation reactions [4,5]. Also, they have been employed as synthons of a wide variety of biologically and medicinally active compounds [6,7], as well as of pharmaceutical compounds having anti-epileptic [8], antibacterial [9,10], anti-inflammatory [10], anticonvulsant [11], antitumor [12] and anti-parasitic activities [13].…”

Chemoselectivity in reactions of hydrazonoyl halides with ethyl 2(3H)‐permidinylideneacetate

“…Furthermore, a recent report from our laboratory on the reactions of 2 with the cyclic ketene aminal indicated that such reactions followed a route that is different from that exhibited by reactions of 2 with acyclic ketene aminals . In the light of these findings and in continuation of our research in the chemistry of hydrazonoyl halides , it was thought interesting to study the reactions of 2 with ethyl 2(3 H )‐permidinylideneacetate 1 , which contains ketene aminal residue, in an attempt to shed some light on their site selectivity. This is because such reactions can theoretically lead to the formation of one or more of the products indicated in Schemes and .…”