Pyrazolo pyrazolium

Several pyrazolo[l,2-a]pyrazoles are prepared by alkylation of pyrazoles with 1,3-dihalo compounds or with malonyl chloride (66FRP1441519 82LA420 86AP70). For example, treatments of 183 with disubstituted malonyl chlorides afford 184. Very similar to this is the formation of pyrazolo[l,2-a]-pyrazolium bromide from 1/f-pyrazoles and bromomethyloxirane (71JHC489 79JOC4473). 

Treatment of the pyrazolium[4,3-r/][l,2,3]oxadiazolium diiodide 124 with -hydroxy- or /)-dimethylaminobenzalde-hyde yielded the pyrazolo[4,3-r/][l,2,3]oxadiazole styryl and azastyryl cyanines 83a and 83b in modest yields. Parallel reaction with -nitrosophenol furnished 83c. Reaction of 124 with 1-ethylquinolinium iodide afforded 84a directly. However, 3-anilinocarbomylmethyl-2,4-diethyl-(N-phenylcarbomylmethyl)pyrazolium(4,3-r/)[l,2,3]oxadiazolium diiodide 125 arising from reaction of 124 with diphenylformamidine in refluxing acetic anhydride, is the precursor to 84b which follows from subsequent reaction with 2-methylisoquinolinium iodide (Scheme 16) <1994MI905-1>. 

The synthesis of a series of l//-pyrazolo[3,4-3]quinoxalines (flavazoles) 55 by acylation, alkylation, halogenation, and aminomethylation of the parent compound was reported and their structures were investigated by H, and N NMR spectroscopy <2005T2373>. Restricted rotation about the partial C-N double bond of the A -acyl derivatives was studied by dynamic NMR spectroscopy and the barriers to rotation were determined. N NMR data of a series of 3-alkyl [aryl]-substituted 5-trichloromethyl-l,2-dimethyl-l//-pyrazolium chlorides 56 (where the 3-substituents are H, Me, Et, -Pr, -Bu, -Pent, -Hex, (CH2)sC02Et, CH2Br, Ph, and 4-Br-C6H4) were reported <2002MRC182>. The N substituent chemical shift (SCS) parameters were determined and these data were compared with the SCS values and data obtained by molecular orbital (MO) calculations. 

Bei 3,5-Dimethoxy-4-phenyl-lH-pyrazol gelingt mit Chlorcarbonyl-phenyl-keten (5 min in Di-ethylether) der RingschluB zu 5,7-Dimethoxy-2,6-diphenyl-l-oxo-lH-(j)yrazolio[l,2-a]pyrazo-liumy-3-olat (Schmp. 150°)2388, analog reagieren eine Rcihe weiterer 1-unsubstituierter 1H-Pyrazole mit Chlorcarbonyl-ketenen oder Kohlensuboxid zu den mesomeren Betain-Strukturen der 1 H--3-olate2389 2399 2400-2403. 

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