Triazines polyazines

Diazines, polyazines, and azapyrylium salts participate in inverse electron demand DielsAlder/retro-DielsAlder-type reactions with electron-rich dienophiles leading to pyridines . 1,2,4-Triazines react with enamines and enol ethers to give pyridines as illustrated in Scheme 162 <2004T6021, 2004CC508>. 

Polyazines like triazine (10) and tetrazine (11) have not been as thoroughly studied as the diazines, however, they make up an important part of the azine literature.1 Triazine has been used to bridge three platinum(II) metals and the X-ray structure of this triplatinum complex has been... 

Absolute electron affinities can be obtained by classification of biological molecules to establish different values of AAG. This is illustrated for riboflavin, vitamin K, vitamin A, polyazines, and hydroxyprimidines. The Ea of these compounds are also predicted by substitution and replacement rules. Those for the dia-zines range from 0.2 eV to 0.4 eV. The values for 1,2,4 triazine and 1,2,4,5 tetrazine are 0.9 eV and 1.7 eV. The replacement of an additional CH by N increases the Ea by 0.6 eV. Therefore, the predicted values for pentazine and hexazine are 2.2 eV and 2.9 eV. The CURES-EC method gives better approximations to these Ea and can differentiate between isomers. 

The product of the cyciization of hydrazones under nitrosating conditions (as described in Section 1.3) is a triazine (rather than a triazole) when the hydrazone is derived from a benzaldehyde instead of an acetophenone [2793]. A mixture of nitrous and acetic acids also gives a triazine [2247, 2646]. Further variations in the product are possible by varying the nitrosating reagent when diethyl azodicarboxylate-acetic acid-nitrous add is used, triazine-4-oxides are formed [2247, 2849]. Recent work on polyazines has been reviewed [3985]. 

An isocyanate reacts readily at ambient temperature with an iminophosphorane derivative of an amidine to form a triazine ring. Recent research on polyazines has been reviewed [3985]. 

Polyazines are polymers with six-membered heteroaromatic rings in the main chain, whereby these rings contain at least one tertiary nitrogen. Compounds which can be conceived by partial hydrogenation of the hetero rings are related to these. Of the very great number of possible different compounds, those with quinoxaline (I), quinazoline dione (II), triazine (III), melamine (IV), and isocyanurate (V) groups have found use in industry ... 

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