Pyrazolinium salts

Elguero Synthesis and reactivity of pyrazolinium salts 76MI40403... 

The salts (71) and (72) are both A -pyrazoline derivatives. However, the first one is obtained by quaternization of a A -pyrazoline and the second one by protonation of a A -pyrazoline (Section 4.04.2.2.2(v)). Several A -pyrazolinium salts (72) and their NMR spectra are described in (69BSF3292,71T123) and for A -pyrazolinium salts (73) see (69BSF3316). 

When two moles of a carbonyl compound are used instead of formalin, the mechanism is different (Scheme 58) (70BSF3147). In one example (80CCC2417) the product of the nucleophilic addition of the hydrazine to the pyrazolinium salt (635 R = = Ph, R = R" =... 

Pyrazoline-5-thiones photoelectron spectroscopy, 5, 205 Pyrazolinium salts reduction, 5, 254 Pyrazolinium salts, 1,2-dimethyl-synthesis, 5, 276... 

The pyrazoline (155) cyclized to the pyrazolinium salt (156) on heating with thionyl chloride (68JOC3941). 

Hurst <93AHC(58)215> has summarized the results of nitration of 1-phenyl-A -pyrazolines for instance, l,5-diphenyl-3-aryl-2-pyrazolines are nitrated by potassium nitrate in sulfuric acid to afford the 1-p-nitrophenyl derivative in quantitative yield. Thermal ring opening of A -pyrazolin-3-carboxylic acids has been used as a method of preparation of )8-aminonitriles <94T7543>, while base-promoted ring opening of 1,1 -disubstituted-3-amino-A -pyrazolinium salts affords either N,N-disubstituted hydrazines or a,)S-unsaturated amidrazones <86SC585>. 

Potassium hydroxide y -Aminonitriles from pyrazolinium salts... 

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