From 3-chloromethyl-1,2,4-triazine 4-oxides to various substituted pyridines and 1,2,4-triazines

An efficient strategy for the synthesis of new pyridine and 1,2,4-triazine derivatives starting from available 6-aryl-3-chloromethyl-1,2,4-triazine 4-oxides was proposed. The deoxygenative nucleophilic hydrogen substitution in the triazine-oxide ring, nucleophilic substitution of the chlorine atom in the side chain, and transformations of the 1,2,4-triazine ring into the pyridine ring via the inverse-electron-demand Diels-Alder reactions, being used in different orders, are a rather flexible tool for the functionalization of the titled heterocycles. The cyanide anion, indoles, thiophenols, amines, and triphenylphosphine were used as nucleophiles. The direct introduction of indole residues into the 1,2,4-triazine ring followed by the substitution of the chlorine atom by a residue of the primary or secondary aliphatic amine was found to be the most convenient method for the library synthesis.