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ChemInform Abstract: A Novel Synthesis of 4‐Pyridazineacetic Acids (V) via Ring Expansion of N‐Cyanomethylated 3‐Pyrazoline‐4‐acetic Acids (IV).

“…The starting materials, 1H-pyrazole-4-acetic acids 1-3, were easily prepared by the condensation reaction of dimethyl and/or diethyl acetylsuccinate with phenylhydrazines, such as phenylhydrazine, 4-nitrophenylhydrazine, and 4-methoxyphenyhydrazine hydrochloride, in moderate to good yields according to the procedure for the preparation of 1a [35] and 1b [36,37] reported in literature (Scheme 2, 1a: 87%, 1b: 88%, 2a: 70%, 2b: 80%, 3a: 75%, and 3b: 86%). The structures of 2a,b and 3a,b were confirmed by elemental analyses and spectroscopic data (IR, 1 H-NMR, 13 C-NMR, and mass).…”

“…Furthermore, in our recent work, we achieved the synthesis of functionalized pyrazoles and dihydropyridazinones via a ring-opening reaction of spirocyclopropanepyrazoles [32]. In keeping with our interest in the chemical reactivity of functionalized pyrazoles [33,34], we focused our attention on the development of a new method for the preparation of pyridazine derivatives starting from 1H-pyrazole-4-acetic acids, because these derivatives are easily available by established synthetic procedures [35][36][37]. Thus, we, herein, wish to report our experimental results, a cyanomethylation and subsequent ring expansion of 1H-pyrazole-4-acetic acids in the presence of a base such as triethylamine and sodium hydride.…”

A Novel Synthesis of 4‐Pyridazineacetic Acids viaRing Expansion of N‐Cyanomethylated 3‐Pyrazoline‐4‐acetic Acids

“…The starting materials, 1 H ‐pyrazole‐4‐acetic acids 1 , 1a , 1b , 2 , 2a , 2b , 3 , were easily prepared by the condensation reaction of dimethyl and/or diethyl acetylsuccinate with phenylhydrazines, such as phenylhydrazine, 4‐nitrophenylhydrazine, and 4‐methoxyphenyhydrazine hydrochloride, in moderate to good yields according to the procedure for the preparation of 1a [35] and 1b [36,37] reported in literature (Scheme , 1a : 87%, 1b : 88%, 2a : 70%, 2b : 80%, 3a : 75%, and 3b : 86%). The structures of 2a , 2b and 3a , 3b were confirmed by elemental analyses and spectroscopic data (IR, 1 H‐NMR, 13 C‐NMR, and mass).…”

“…The elemental analyses were performed on a YANACO MT‐6 CHN analyzer. The starting compounds, 1 H ‐pyrazole‐4‐acetic acids 1a [35], 1b [36,37], 2a , 2b and 3a , 3b were prepared in this laboratory according to the procedure reported in literature [35–37].…”

“…Furthermore, in our recent work, we achieved the synthesis of functionalized pyrazoles and dihydropyridazinones via a ring‐opening reaction of spirocyclopropanepyrazoles [32]. In keeping with our interest in the chemical reactivity of functionalized pyrazoles [33,34], we focused our attention on the development of a new method for the preparation of pyridazine derivatives starting from 1 H ‐pyrazole‐4‐acetic acids, because these derivatives are easily available by established synthetic procedures [35–37]. Thus, we, herein, wish to report our experimental results, a cyanomethylation and subsequent ring expansion of 1 H ‐pyrazole‐4‐acetic acids in the presence of a base such as triethylamine and sodium hydride.…”