Pyridones, N-oxides and related compounds betainoid rings

4 Pyridones, N-oxides and related compounds betainoid rings 

Three types of compound can be considered (see Section 2.2.1.2) to be derived from a cationic ring carrying a negatively charged substituent (7)  

These compounds all contain both an electron source (Y ) and an electron sink (Z+). Furthermore, their aromaticity is significantly reduced by the non-uniform electron distribution. Hence they are highly reactive. The orientations of the reactions of these compounds with electrophilic and nucleophilic reagents are deducible from their canonical forms (see structures 12-14). 

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