1.3.5- Triazine azido-, photolysis

The highly electrophilic 1,3,5-triazinylnitrene generated by photolysis of 2-azido-4,6-dimethoxy-l,3,5-triazine (24) does, however, bring about ring expansion of benzene to l-(4,6-dimethoxy-1,3,5-triazin-2-yl)-1//-azepine (25) in moderate yield.168... 

Azido-4,6-dichloro-133-triazine 35, matrix isolated in argon at 10 K, yields triplet nitrene 36 and the strained cyclic carbodiimide 37 upon photolysis <99CC2113>. 

As shown in Section II,C,l,b, photolysis or thermolysis of l-azido-8-arylazonaphthalenes gives rise to heterocyclization of these compounds, resulting in a mixture of mesoionic derivatives of naphtho[rf ]triazine 233... 

Nitrotriazines are formed by photolysis of azido-l,3,5-triazines in GHG13 or MeCN in the presence of air (Scheme 91). 

Intramolecular carbenoid and nitrenoid insertions are also quite effective for the preparation of peri-condensed heterocycles. Thus, photolysis of 1-naphthyl-1,2,3-triazoles 113 leads to bcnzo[d,e quinolines 115, possibly via carbene intermediate 114 (Scheme 55) <1987J(P1)413>. Similarly, on photolysis or thermolysis of 8-azido-l-arylazonaphtha-lenes 116 naphtho[l,8-<7, ]triazine derivatives 117 are formed along with A-aryhminobenzo[/y/]indazoles 118 (Scheme 56) <1978JOC2508, 1982JOC1996>. 

New fused tetrazoloazines that have been reported include tetrazolo[5,l-a]isoquinolines,665 tetrazolo[5, l-6]benzothiazoles,666 and tetrazolopyridines.667 Reactions of fused tetrazoloazines, or the azido isomers, that have been reported include hydrolytic cleavage of the pyrimidine ring of tetrazolopyrimidines,66 pyrolysis of 3-azido-pyridazine 2-oxides,66 and photolysis of azido-l,3,5-triazine.670 Dipole moments of 3-azido-1,2,4-triazole derivatives have also been reported.671... 

Photochemical properties of azido derivatives of six-member aza-heterocycles (pyridine, pyrimidine, triazine, quinoline, acridine) are discussed. Data on the stmcture of the reaction products formed under photolysis of azides in different conditions (solvent, temperature, additives), and also data on the matrix isolation spectroscopy of heterocyclic nitrenes, including high-spin nitrenes, produced by low-temperature photolysis of the corresponding azides are shortly examined. 

In the series of azido-l,3,5-triazines, a similar trend was observed. Photolysis of azidotriazines such as 105 yielded only typical nitrene-derived products, whereas products indicative of dehydrotetrazepine formation were not observed. " In acetonitrile solution, an interesting cycloaddition of the nitrene 106 to the solvent was observed that led to pyrazolotriazine 107, which subsequently rearranged further. ... 

The photochemistry of azidotriazines depends on substitution. Photolysis of 2-azido-4,6-dichloro-1,3,5-triazine 108, matrix-isolated in Ar at 10 K, led to formation of both triplet nitrene 109 and didehydrotetrazepine 110, which could be interconverted photochemically. Extended photolysis, however, resulted in the formation of an unidentified ring-opened product." Laser flash photol) is experiments indicate that both 109 and 110 are formed at ambient temperature." ... 

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