Doubly charged heterocyclic systems

Table 14. lH NMR Parameters of Doubly Charged Heterocyclic System of THF—d8 179). 

Ty, Table 15. 13C NMR Parameters of the Doubly Charged Heterocyclic Systems in THF 179>. 

Table II. Spectral Patterns and HOMO-LUMO Energy Gaps of Doubly Charged Heterocyclic Systems as Disodium Salts in THF-dg at Room Temperature...

Mass spectral data have frequently been used in the structural determination of boron heterocycles. One paper has been devoted to the mass spectra of some six-membered boron-nitrogen systems. It was concluded that the spectra could be interpreted analogously to their hydrocarbon counterparts. In all cases the molecular peak was the base peak of the spectrum (68T6755). Doubly charged molecular ions, a feature typical of aromatic compounds, are often encountered. It should be noted, however, that some certainly non-aromatic aminoboranes give such doubly charged ions as well. 

Fused benzenoid heterocyclic systems including quinoxaline derivatives in an ether solvent are reduced by sodium to the corresponding antiaromatic doubly charged species <85JA1501>. These dianions represent a new class of charged species, viz., nitrogen-containing polycyclic anions. 

One of the main problems in assigning aromatic or antiaromatic character to a system is the relativity of these terms and consequently the need for proper reference compounds. Our approach overcomes this difficulty by using the neutral parent compounds as reference compounds they are good reference compounds because they differ merely in their electronic structure. Therefore, doubly charged 4n tt electron compounds are good model compounds for antiaromaticity studies. Because carbocyclic and heterocyclic dianions can be prepared from stable precursors and because they sustain moderate stability, they were selected for this study. 

Pseudo-aromatic Boron Heterocycles.—mass-spectrometric study of isotopic-ally labelled arylborazines has revealed a tendency to produce doubly charged ions. The compounds (24) and (25) are new boron heterocyclic systems. Boroxaphenanthrenes such as (26) are useful as antioxidants for lubricating oil.i ... 

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