Ethanolic solutions of the hydrochlorides of the mostly new 2(4),5-dihydro-1,2,4-triazines (1)-(4) were irradiated with a high-pressure mercury immersion lamp (λ ≥ 300 nm). The salts (Ia)-(3a) underwent reductions, ring contractions, and dehydrogenations upon irradiation to yield pyrazoles (5) and (6) along with phenanthroimidazoles (9) and (10). In addition, the 4-methyl-3,5,6-triphenyl-4,5-dihydro-1,2,4-triazinium chloride (3a) furnished the 6-(1-hydroxyethyl) adduct (11) whose structure was assigned on the basis of its 1H and 13C n.m.r. spectra, and an X-ray diffraction study. The 4-(3-hydroxypropyl)dihydrotriazinium chloride (4a) led, in addition to the expected pyrazole (5), to two new products: the aromatic triazine (15) and the oxazinotriazine (21) by photoelimination and intramolecular photosubstitution, respectively.
|Number of pages||8|
|Journal||Journal of the Chemical Society, Perkin Transactions 1|
|Publication status||Published - Dec 1 1988|
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