engleski

Conformational isomerism and tautomerism in 1, 2-dihydro-1, 3, 5-triazines – an experimental and theoretical study

Recently, we prepared a series of novel triguanide derivatives which were subsequently established to undergo a cyclisation reaction yielding the appropriate 1, 2, 4, 6-tetrasubstituted 1, 3, 5-triazines. Since the ubiquitous 1, 3, 5-triazine unit has found its application in many fields of research ranging from material science to pharmaceuticals, a research on the electronic and structural characteristics of triazines provides a better understanding of the principles governing their reactivity and allows a rational design of new triazine-based compounds with improved properties. With respect to their structure, 1, 2, 4, 6-tetrasubstituted triazines can exist in several tautomeric forms of which the 1, 2-dihydro is the most stable one. We report on the variable temperature solution NMR study of conformational isomerism in 1, 2-dihydrotriazine 1 and its perchlorate salt [1H]ClO4 and show how the computationally predicted results correlate with the experimentally observed ones. Both neutral and cationic species display a rotational barrier as a function of the state of protonation. Such behaviour is found to be associated with a resonance stabilisation of the molecular framework which further enhances upon protonation at the exocyclic imino nitrogen atom.

conformational isomerism; tautomerism; 1; 2-dihydro-1; 3; 5-triazines

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