Pyridazines electrochemical

Pyrrole derivatives substituted in positions 1-, 3-, or 4- have also been electrochemically polymerized (positions 2- and 5- must be free for polymerization). Besides homopolymers, copolymers can also be prepared in this way. Other nitrogen heterocycles that have been polymerized by anodic oxidation include carbazole, pyridazine, indole, and their various substitution derivatives. 

Morozov and co-workers electrochemically demonstrated the pyridazine ring fragmentation induced by electron transfer agents. This reaction proceeded by elimination of chloride ions, cleavage of the pyridazine ring, and the formation of phthalonitrile 202 from 201 <00MC34>. 

Ru(0)(Rj-dppi)(tpy)] (R3-dppi=R3-3,6-bis(6-chloropyrid-2-yl)pyridazine with R=H, Me, Cl) is probably the species generated by cyclic voltammetric oxidation of [Ru(H30)(R2-dppi)(tpy)] ". The reagents [Ru(0)(Rj-dppi)(tpy)]Vwater pH 7 electrochemically oxidised benzyl alcohol to benzaldehyde. Second-order rate constants were determined and a mechanism proposed which involves pre-association of the substrate with the Ru(lV) complex [679],... 

The reduction of a number of pyridazines was treated in Part I1 later electrochemical investigations296 confirmed that the initial reduction consumed two electrons and the primary product was suggested to be 1,2-dihydropyridazine, which tautomerized to the 1,4-dihydro derivative hydrolysis with ring opening followed. 

Alkylation of pyridazino[4,5- i]pyridazines is possible by electrochemical reduction in THF at — 1.2 V in the presence of methyliodide to afford the 4,5-dimethyl derivative quantitatively... 

Lund studied the electrochemical reduction of substituted pyridazines and reported that reduction of 3,6-diphenylpyridazine gave the 1,4,5,6-tetrahydro derivative 75.130 This is probably produced through the intermediacy of 4,5-dihydropyridazine 28a since, according to Lund, neither the 1,2- nor the 1,4-dihydro tautomers are expected to be reduced further under the reaction conditions used [Eq. (20)]. 

Novel pyrrole C-nucleosides 233 were synthesized in two steps by cycloaddition of alkynyl C-nucleosides 231 to dimethyl l,2,4,5-tetrazine-3,6-dicarboxylate 150 <1994AP365>, followed by extrusion of nitrogen from the resultant pyridazine C-nucleosides 232 using electrochemical and/or chemical reduction (Scheme 59) <2004TL1031>. 

Yasuda, T, Y. Sakai, S. Aramaki, and T. Yamamoto. 2005. New coplanar (ABA)n-type donor-acceptor TT-conjugated copolymers constituted of alkylthiophene (unit A) and pyridazine (unit B) Synthesis using hexamethylditin, self-organized solid structure, and optical and electrochemical properties of the copolymers. Chem Mater 17 6060-6068. 

Van et al. [197] studied the electrochemical behavior of pyridazine using cyclic voltammetry in acetonitrile with different supporting electrolytes. Dark, greenish-blue polypyridazine formed on the anode when either lithium perchlorate or ammonium tetrafluoroborate was used as the supporting electrolyte. Also investigated were variations in the acidity of the solution during the course of electrolysis and the effects of the synthetic conditions on the electrochemical and other properties of the films. The pyridazine rings are believed to be para linked and the perchlorate or tetrafluoroborate counteranions are present in a 2 1 molar ratio. Two isomers of pyridazine—pyrazine and pyrimidine—could also be oxidized, but these isomers yielded only yellowish, powdery precipitates and no films. 

Brown neutral polypyridazine can be prepared by electrochemical undoping of the oxidized polymer [198]. The undoped polymer has a band gap of about 1.8 eV. The infrared spectrum has features similar to that of the monomer, in addition to peaks that can be assigned to para-substituted pyridazine. Chemical analysis is consistent with the repeat formula, C4N2H2. 

Heterocyclic Compounds. All the heterocyclic compounds, unsubstituted by electroactive groups, from which radical ions have been obtained by electrochemical generation are nitrogen heterocycles. Among the numerous systems involved radical anions have been obtained from pyrazine [118], pyridazine [126], and tetrazine [126], and radical cations have been obtained from dihydropyrazine [126-128] and dihydrotetramethylpyrazine [128]. 

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