Synthesis of new polyfunctionally substituted pyridazines, phthalazines, cinnolines and thieno[3,4-c]pyridazines

Abstract

The reaction of ethyl 2-arylhydrazono-3-oxobutyrates (Ia, Ib) with active methylene ketones afforded pyridazin-5-carbonitrile derivatives. The methyl function in the ethyl pyridazin-3-carboxylate derivatives IIa, IIb reacted with arylidenemalononitrile to yield the phthalazine derivatives Va-Vf and with elemental sulfur to yield the thienopyridazines XIXa, XIXb. The cinnolines are producted from reaction of IIa, IIb with diethyl acetonedicarboxylate.

Heterocyclic Synthesis with Enamines: Convenient Syntheses of Polyfunctionally Substituted Pyrazole, Pyridine, Pyrimidine and Pyrazolo[3,4‐d]pyrimrdine Derivatives

“…Compound 18 coupled with benzenediazonium chloride in ethanolic sodium acetate solution at pH 8 to afford the corresponding phcnylhydrazono derivative 19. 13 . 14 However, 19 was an unstable red product that decomposed autocatalytically at 25°C under the action of light within two days; therefore it must be stored in a refrigerator.…”

Optimizing Scale Up Yield to Pyridazines and Fused Pyridazines

“…However, beginning in 1988 Elnagdi et al [19,[31][32][33][34] reported several syntheses of phthalazines via reactions of alkyl pyridazinyl carbonitriles 55 with a variety of reagents. In 1989 Elnagdi et al reported that the pyridazinone 59 reacts with sulphur to yield the bicyclic thiophene 60 and that the latter substance underwent 4+2 cycloaddition with alkenes and alkynes to afford phthalazines 63 (Scheme 17) [19,35,[40][41][42][43]. This type of process has been reported by several authors, proving its general nature [35][36][37][38][39].…”

Arylhydrazonals as aldehyde components in Baylis-Hillman reaction: synthesis of 5-hydroxy-2,3,4,5-tetrahydropyridazine-4-carbonitrile and 6,7,8,8a-tetrahydrocinnolin-5(1H)-one

“…Thus, the mass spectrum of 4a revealed molecular ion peak as base peak at m/z 311; IR showed OH at 3340 cm -1 ; 1 H NMR revealed doublet signals at 3.61 and 6.40 for pyridazine H5 and OH respectively, multiplet signal at 3.87 for pyridazine H4 and doublet of doublet signal at 4.51 and 4.94 for pyridazine H3. Also 13 …”

“…[1][2][3][4][5][6][7][8][9][10] In the past our group could successfully utilitized arylhydrazonals as precursors to pyridazines and pyrazoles with unique substitution pattern. [11][12][13][14][15][16] …”