Pteridin-4 -pyrimidinones

Rearangement of furoxans leads to the formation of new heterocyclic systems derivatives of triazoles, diazoles, isoxazoles, and pyrimidinones. For example, on the basis of the experimental results using labeled compound 52-15N , the formation of 8-phenyltheophylline 53, the 1,3-dimethylalloxazines (54 n = 0, 1), and l,3,7,9-tetramethyl-l//,9//-pyrimido[5,4-g]-pteridine-2,4,6,8-tetraone 55 in the thermal reaction of the iV-oxide 52 with benzylamine, aniline, or piperidine and the generation of NO or NO-related species in the reaction with iV-acetylcysteamine were reasonably explained by... 

These compounds are also known as thiapteridines. Most syntheses of pyrimido[5,4-/>] [l,4]thiazines were developed for pteridines and then adapted for the thio analogues. Thus, the cyclization of polyfunctionalized pyrimidinones (e.g. (268) - (269)) is a well-known method (Equation (41)) <92H(34)729>. 

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