Pyridazinium 4-dicyanomethylides

Pyridazinium dicyanomethylide gives a mixture of the pyrazole (38) and the substituted cyclopropene (39 Scheme 13). 

S-N rearrangement, 3, 36 ionization constants, 3, 4 oxidation, 3, 37 quatemization, 3, 17 Pyridazine-3 (2 H) - thiones analysis, 3, 2 tautomerism, 3, 5 Pyridazinium betaine, 3-oxido-photolysis, 3, 11 Pyridazinium betaine, 5-oxido-photolysis, 3, 11 Pyridazinium dicyanomethylide photolysis, 3, 12... 

Pyridazine N-oxides and ylids react with benzyne (Scheme 3). Pyridazine N-oxide gives a mixture of the 1-benzoxepin (153) and arylpyridazine (154) via the 1,3-cycloadduct (152). N-Acetylpyridazinium imide forms an isolable cycloadduct (155) which is transformed by heat or sodium methylate into 156 and 157. The cycloadduct (158) from pyridazinium dicyanomethylide under similar reaction conditions is aromatized to 159. ... 

Irans-Styrylpyridazines are photoisomerized into cis-isomers, which could be separated from the photostationary equilibrium mixture. Photolysis of the pyridazinium dicyanomethylide 285 gives a mixture of a pyrazole (286)... 

Pyridazinium and phthalazinium dicyanomethylides give indolizines as primary adducts with 1,2,3-triphenylcyclopropene, either by [4 + 2] cycloaddition or by 1,3-dipolar addition of the ylide to triphenylcyclopropene (81JCS(P1)73). 

Both products are thought to be derived from an initial adduct (320) but the detailed mechanisms are very unclear 252). Similar products are obtained from pyridazinium, phthalazinium and pyrazinium dicyanomethylides 252). 

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