4-Amino-1,2,3-triazoles photolysis

Photolysis reactions of 5-amino- or 5-alkoxy-substituted triazolines have not been studied extensively usually they yield triazoles (Section IV,A,3). 

Irradiation of 2H-1,2,3-triazoles (91) in ether gives 22% MeCN, and in the presence of excess cyclopentene it affords the adduct (92) (68CC977). 4H-Triazolines (93) bearing methoxycarbonyl and alkyl groups at the j3 -position give, on thermolysis, 2H- 1,2,3-triazoles (94) and/or 3-amino-2i/-azirines on photolysis, only azirines are formed (80CC940). 

The enamine-azide 1,3-dipolar cycloaddition has been found to be thermally reversible, e.g. (282) (283) (tsjhcsos). 4//-Triazoles (284), formed from sodium azide and a-chloroenamines bearing methoxycarbonyl and alkyl groups at the /3-position, give on thermolysis aromatic triazoles (285) and/or 3-amino-2//-azirines (286). On photolysis only azirines (286) are obtained (8occ94o). 

Other evidence to support nitrene formation is the identity of the reaction products obtained when nitrenes are generated by independent methods. For instance, N-nitrenes of 1,2,3-triazoles can be generated by oxidation of 1-amino-u-triazoles (88M1041), on photolysis of their potassium tosylates (134) (64AG144), or by decomposition of unstable lithium salts of l-(l,2,3-triazole-l-yl)-4-p-tolylsulfonyl-tetrazenes[72JCS(Pl)1315] [Eq. 

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