2- azaallenium salts

A/-Acylimino compounds are converted by oxonium salts to iminium salts, which can be regarded as azaallenium salts. " A lot of lactams have been alkylated by oxonium salts at the carbonyl oxygen to give salts of type (70 equation 43)7-i0.199-207... 

An azaallenium salt has been prepared by treatment of bis(iminomethane) compound with Tf20 (eq 78). ... 

Cationic cumulenes are also known, and especially the azaallenium salts are known for their 1,3-dipolar character. These cationic cumulene salts undergo numerous [3-1-2] cycloaddition reactions with suitable dipolarophiles to give five-membered ring heterocycles, often in quantitative yields. 

Azaallenium salts, such as RC(C1)=N+=C(C1)R SbClg, react with carbodiimides to give labile 2,2-dichloro-l,3,5-triazinium salts 180 . 

The linear 2-azaallenium salts, C=N+=C, have electronic stmctures similar to cumulenes and their infrared spectra show the typical cumulene bands at 1870-1910 cm ... 

One example of the cycloaddition of a 2-azaallenium salt 15 with diphenylacetylene is known, and the cycloadduct, 1 l//-indeno[l,2-c]isoquinoline salt 16, is obtained in 37 % yield... 

The vinyl substituted 1,3-dichloro-2-azaallenium salt 17 undergoes cyclization on heating to give the thiazinium salt 18 in 90 % yield. ... 

When the 2-azaallenium salts 20 are generated from the A-alkylnitrilium salts 19 and dithiomethylacetylene they undergo cyclization to give the 2//-pyrrolium salts 21 . 

In the reaction of l-oxa-3-azabutatriene salts with ketones and aldehydes, 2-azaallenium salts and carbon dioxide are obtained... 

A straightforward synthesis for [l,2,4]triazolo[2,3-c][l,3,5]oxadiazinium salts has been described by Hamed et al. <1995JPR274>. The transformation of azaallenium hexachloroantimonate 98 with benzhydrazone was carried out in dichloroethane under reflux conditions to yield the fused quaternary salt 99. 

The ethylene bromonium and 1-bromoethyl cations and their neutral and anionic counterparts have been the subject of a tandem mass spectrometric study of dissociation and gas-phase redox reactions. IR and Raman studies of the bioactive bromonium cation (19), as its hydrogensulfate salt, agree with the results of an X-ray structure determination, and theoretical calculations are also in agreement, except for the details of the NO2 groups. The azaallenium ion (22) is an intermediate in the photolysis of (20) (21) and (22) could both be seen. Flash photolysis of (23) leads to (24), (25), and (26), all of which could be trapped by nucleophiles (27) was not an intermediate. NMR lineshape analysis of the spectmm of (28) leads to reaction rate constants of formation for both the intimate ion pair (29) and the solvent-separated ion pair (30). ... 

The structures of the 2-oxazolinium, 1,3,5-oxadiazinium and 3-azapyrylium salts obtained by means of electrophilic catalysis by acylium ions102,113 point to the fact that their formation proceeds not via Af,7V-bis-acyliminium ions 332 and 333, but via the TV-acyliminium ions 322 (i.e. those protonated at the nitrogen atom). In our opinion142, the acetoxy azaallenium ions 335 can be transformed to the Af-acyliminium cations 337 by a deacylation to the N-acylimines 336, followed by protonation of the latter (equation 91). Such a process is quite possible under the conditions used for... 

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