Aromatization of six-membered rings

The aromaticity of six-membered rings is discussed in Section 2.2.4.2. In general most of these compounds tend to react typically by substitution rather than addition, i.e. they tend to revert to type. However, ring oxygen atoms, an increasing number of ring heteroatoms, benzannulation and ring... 

Aromatic substitution (see Substitution reactions at aromatic carbon atoms) Aromatization of six-membered rings Titanium(IV) chloride-Diethylaluminum chloride, 309... 

As a particular case of the substitution in nucleic acid bases, the insertion/ addition of a benzene ring to the natural bases can be considered (Scheme 30 2006JPCA(110)12249). The analysis of the local aromaticity, expressed by HOMA, NICS, FLU, and PDI indices, revealed notable differences in the aromatic character of the natural and size-expanded bases. Insertion/ addition of the benzene ring reduces aromaticity of six-membered rings in natural bases as well as the aromatic character of the benzene ring. An inverse correlation between the HOMO-LUMO gap and the aromaticity of the fused benzene ring was also found. Therefore, it has been su ested that... 

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