Photochemistry of N-heterocycles, 5 - A comparison of chemical and photochemically induced reduction of some 2(4),5-dihydro-1,2,4-triazines and aromatic 1,2,4-triazines

Chemical reduction (Zn/AcOH) of the arene 1 and of 2(4),5- dihydro-1,2,4-tr iazine 7 has been reinvestigated, resulting in the amendment of Literature data concerning this reaction. Chemical, electrochemical, and photochemical ly induced reductions and ring contractions of 1,2,4-triazine derivatives T he first example of a triaryl-1,4- dihydrotriazine has been prepared. Some further evidence is presented that supports the proposed mechanism of the p hotochemically induced reduction and ring contraction of 1,2,4-triazines.ha ve been compared.