2-(3-Chloro-5,6-diphenyl-2,5-dihydro-1,2,4-triazin-5-yl)-2-methyl-propane-nitrile.

The title compound, C(19)H(17)ClN(4), was obtained from the reaction of 3-chloro-5,6-diphenyl-1,2,4-triazine with isobutyronitrile in the presence of lithium diisopropyl-amide as an unexpected product of covalent addition of isobutyronitrile carbanion to the C-5 atom of the 1,2,4-triazine ring. The 2,5-dihydro-1,2,4-triazine ring is essentially planar (r.m.

5,5',6,6'-Tetra-methyl-3,3'-bi-1,2,4-tri-azine.

In the title compound, C(10)H(12)N(6), the two 5,6-dimethyl-1,2,4-triazine halves of the mol-ecule are related by a centre of symmetry. The two triazine rings are coplanar to within a maximum deviation of 0.013 (2) Å from the mean plane of the ring atoms.

Pyrazolo[4,3-e][1,2,4]triazines: purine analogues with electronic absorption in the visible region.

Synthesis of several pryrazolo[4,3-e][1,2,4]-triazines is described. The absorption spectrum of some 5-substituted derivatives was found to extend to the visible region. These compounds were found to inhibit some enzymes of purine metabolism, like xanthine oxidase or bacterial purine-nucleoside phosphorylase with Ki values in the 10(-3) -10(-5) M range.

Tandem vicarious nucleophilic substitution of hydrogen/intramolecular Diels-Alder reaction of 1,2,4-triazines into functionalized cycloalkenopyridines.

Synthesis of 2,3- and 3,4-cyclopentenopyridines, 5,6,7,8-tetrahydroquinolines and 5,6,7,8-tetrahydroisoquinolines from 1,2,4-triazine derivatives is reported. Introduction of an alpha-functionalized methyl substituent (e.g.