Cascade reactions for constructing heterocycles containing a pyrimidino-pyrazino-pyrimidine core using 1,2,4-triazole scaffolds.

• Aminoethyl-1,2,4-triazoles react with glyoxal to form new heterocyclic core. • This core is an dodecahydropyrimido[1′,2′:4,5]pyrazino[1,2- a ]pyrimidine. • Formation of one "pyrazino-pyrimidine" was clarified by X-ray analysis. The regioselective cyclocondensation of aminoethyl-1,2,4-triazoles and glyoxal provides pentacyclic heterocycles in which two 7,8-dihydro-5 H -6λ2-[1,2,4]triazolo[1,5- c ]pyrimidine systems are connected through CH(OH) bridges generating a central piperazine-2,5-diol ring. The structure of the new compounds was elucidated based on 1H, 13C and 15N NMR spectroscopic methods. The molecular structure of the parent compound generated from aminoethyl-1,2,4-triazole was established by single crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]