Photochemistry of N-heterocycles. Part 3. Synthesis and photochemistry of some new dihydro-1,2,4-triazines and their quaternary salts

Abstract

Several new dihydro-1,2,4-triazines, 1b, 4, 5, 16 and 19, have been synthesized and their structures unambiguously determined. The existence of 1,2- and 1,4-dihydrotriazines, 20 and 22, described in the literature was ruled out. Irradiation of the aromatic triazines 6 and 15 and the novel quaternary dihydro-1,2,4-triazinium salts 4, 5, 19 furnished new evidence for both the reduction pathways and the mechanism of ring -contraction reactions.