Imine-imide tautomerism

Phenytoin and barbiturates display tautomerism of the imine-imide type, as shown in Figure 3.16. The predominant tautomer is the imide form, although some older textbooks list the structure of the drug as the minor tautomer. 

The monomer VAm is not available due to the well known tautomerization equilibrium with acetaldehyde imine. Therefore, polymer-analogous reactions must be employed to synthesize PVAm from suitable precursor polymers, e.g. poly(acrylamide) [53, 54], poly(vinyl acetamide) [55], poly(vinyl carbamate) [56], or poly(vinyl imides) [57]. Some of these polymer-analogous reactions require rather rigorous reaction conditions and side-products and degraded polymer chains disturb the properties of the final product. 

Dimethoxy-U4,2,4,6-thiatriazine 1-imides (for tautomerism see Section 2.1.1.3.) are oxidized to 1 x6,2,4,6-thiatriazin-l-imine 1-oxides 8.3... 

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