Formamidines amines with 1,3,5-triazin

Nucleophilic attack at the fully conjugated 1,3,5-triazine usually results in ring cleavage. Thus, active methylene compounds react with 1,3,5-triazine in aminomethylenation reactions. A three-component reaction of cyclopentadiene with 1,3,5-triazine and a secondary amine leads to /V,7V-di substituted pentafulven-6-amines (304) and N2-(6-pentafulvenyl)formamidines (305)... 

When the dihydro-1,2,4-triazinone (194) is heated at 180 °C under reducing conditions there is rupture of the 1,2-bond followed by ring closure, producing 4,5-diphenyl-imidazolinone (195). Such reductive ring closures of benzotriazine 1-oxides (196) can give benzimidazoles, in particular 2-(4-thiazolyl)benzimidazoles (197) ( thiabendazole ). Similar reactions take place with 1,3,5-triazines. In fact, primary amines cleave the compounds completely with evolution of ammonia and formation of iV.iV -disubstituted formamidines. With suitable primary amines, though, this reaction can be designed to produce imidazolines or benzimidazoles (Scheme 113). 

Anilines and heterocyclic amines react with 1,3,5-triazine to furnish formamidines, e.g. (363) and (364) (Scheme 64). CH2-acidic compounds, e.g. nitriles, can be formylated by heating with 1,3,5-triazine. In the course of such reactions the enamines thus obtained can be converted to formamid-... 

Triazine is inert towards electrophiles. However, nucleophilic attack occurs easily and opens the ring, but in the case of alkyl- and aryl-l,3,5-triazines, only under forced conditions. Typical examples are the reaction of 1,3,5-triazine with primary amines leading to ring fission of the heterocycle into formamidine units 1,... 

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