Azidinium salts

Diazoalkanes and related compounds are not suitable guests for the types of hosts discussed above. Very weak complexation was found with diazodicyanoimidazole (2.53 Sheppard et al., 1979) in which the mesomeric zwitterionic structure with a formal diazonio group (see Secs. 2.6 and 6.2) is dominant. However, no complexation was found for another compound with a formal diazonio group, the ben-zothiazol-azidinium salt 2.50 (Szele and Zollinger, 1982). 

The synthesis of azidocycloimonium fluoborates, compounds which possess a quasi-aromatic heterocyclic nucleus, has been reported by BalU and Kersting . Halogen atoms adjacent to quaternary nitrogens in heteroaromatic salts such as 154 157 undergo replacement by azide ion at low temperatures to produce the resonance stabilized azidinium salts (158). On the basis of infrared studies and reactivity towards nucleophiles, Balli has suggested that these salts are best considered as iV-diazonium compounds... 

Another type of azides which can serve as diazo donors is the azidinium salts of the general formula 100. The important advantage... 

Triazenes such as 122 are obtained in the reaction of azidinium salts with sodium azide. The reaction proceeds via an intermediate... 

Diazo transfer to pyrazolidone (39) using azidinium salt (38) affords diazo pyrazolidone (41) and imine 40 this method has proved superior to the aryl sulfonyl azide reactions in cases where azo coupling occurs. 

Consecutive azo coupling is, however, also possible if azidinium salts are used as transfer reagents, and heteroaromatic enols, aromatic or heteroaromatic amines as substrates (Balli and Gipp, 1966 Balli and Felder, 1978 Balli et al., 1994). An example is the reaction of 5-methyl-2-phenyl-3,4-dihydropyrazol-3-one (2.153) with the azidinium salt 2.144 (2-63). At pH 3-4 the 4-diazo derivative 2.154 is formed, but... 

We claim, however, that this reaction is likely to be more complex. The isolated intermediate salt may be the prototropic isomer 4.23 formed intermolecularly from 4.21, which is the primary steady-state intermediate. Compound 4.23 is energetically more favorable because in 4.23 — in contrast to 4.21 — conjugation (Ti-orbital overlap) between the arylcarbonyl part and the 4-toluenesulfonyl azide part is not interrupted by an sp C-atom. Intermediate 4.21 may, however, also react directly to give the diazoketone 4.22 via a cyclic transition state 4.24 that contains, however, a less favorable (Z)-azo group. The prototropy 4.21 4.23 was included at an early date for the mechanism of the diazo transfer from 4-toluenesulfonyl azide to the cyclopentadienyl anion by Roberts (see review Roberts, 1990, p. 217) and by Huisgen (1990). A transition state similar to 4.24 was mentioned by Balli et al. (1974) for the diazo transfer of azidinium salts to pyrazolin-5-one and 5-aminopyrazole compounds (see below). 

C,HrXN-N(C,H,)2 N-Amino phenyl-aziridine Girard reagents Tosylhydrazine HN NH Alkyl azides Picryl azide Cyanogen azide Ng, Dicyclohexyl-ammonium azide Guanidinium azides Azidinium salts HNs NH2OH... 

Diethylamine acetate Pyridiniiim salt T etramethylammonium acetate, Tetraethyl-ammonium-Piperidinium acetate Isoxazolium salts Trialky loxonium salt Amidinium salts Ketenimines Diazo compounds Diazomethane, Phenyl-diazomethane K-methy Idiazotate Hexamethylenetetramine Azo compounds Azodicarboxamide ROOC-N N-COOR A zodiisobuty ronitrile T riazenes Azidinium salts p-Nitrobenzene-diazonium sulfate Sulfanilic acid, diazotized... 

Azidinium salts p-Nitrobenzene-diazonium sulfate Sulfanilic acid, diazo tized... 

Picryl azide Tosyl-Cyanogen -Nf, NH Ng, Dicyclo-hexylammonium azide, Bu N Ng-Guanidinium azides Azidinium salts HNg... 

Several years ago Balli developed an ingenious method for generating ylids which did not depend at any stage on deprotonation of a cation Treatment of certain azidinium salts with azide ion yielded 3 moles of nitrogen and an ylid (equation 5) which could be... 

A zodicarboxamide ROOC-N N-COOR A zodilsobutyronitrile Triazenes Diazonium fluoro-borates (30) Azidinium salts p-Nitrobenzene-diazonium sulfate Sulfanilic acid, diazotized... 

Azidinium salts s. Azido-cyclimmonium salts Azidoaldonic acid lactones... 

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