2- -2//-benzo l,2,3 triazoles

As shown by Heindel and Corley (1979), ring closure also takes place if the nucleophilic nitrogen is part of a heterocycle, as in the diazotization of 5-amino-3-methyl-2-H-l,2,4-benzothiadiazine-l, 1-dioxide (6.50). In the tricyclic compound 6.51 formed initially, the thiadiazinedioxide ring is opened rapidly in water, forming 1-acetyl-7-aminosulfonyl-l-i/-benzo-l,2,3-triazole (6.52). 

Potassium /V-mtrosohvdroxv lam inc-/V-sul 1 onatc. 4662 Potassium 1-phenylethanediazoate, 2964 Potassium O-propionohydroxamate, 1210 Silver benzo-l,2,3-triazole-l-oxide, 2127... 

Substituted benzo-l,2,3-triazole 1-oxides were known when the first noncondensed 3-substituted 1,2,3-triazole 1-oxides 456 were reported in 1987 and it was shown that a compound believed to be the isomeric 1-benzyloxy-l,2,3-triazole was in fact the triazole 1-oxide 456 (R=CH2Ph) (1987ACSA(B)724). Since then about 60 3-substituted 1,2,3-triazole 1-oxides with a variety of substituents at C3, C4, and C5 have been reported. No previous review on 3-substituted 1,2,3-triazole 1-oxides exists. Examples of the use of 3-substituted 1,2,3-triazole 1-oxides 448 by synthesis of substituted 1,2,3-triazoles are given in (1988BSB573). 

Concerning the transformation of substituents, a special note should be made on a series of ring-closure reactions carried out on the side chain of some [l,2,4]triazolo[4,3-r]benzo[l,2,3]triazines published by Moustafa <2001SC97>. The results are summarized in Scheme 18. This scheme shows that by transformation of the R group attached to the sulfur atom of derivative 97 a fairly large set of cyclic products - involving thiazolidone 97a, [l,2,4]triazole 97b, coumarone and its imine 97c and 97d, respectively, benzoxazylpyrane, 97e, thiophene 97f, and cyclopenta- or cyclohexa-fused protected pyrone 97g substituents - have been obtained. 

UV irradiation of 2-arylbenzotriazoles (144), including the commercially available photostabilizer Tinuvin P, in an aerated solvent results in oxidation of the benzo ring to give the 2-aryl-l,2,3-triazole-4,5-dicarboxylic acid (146), possibly via the intermediate 2-arylbenzotriazole-4,7-dione (145) (Scheme 25). Indeed, when the independently synthesized l-phenyl-2. -benzotriazole-4,7-dione (145, R = = H) is irradiated under the same conditions, compound (146 R = R = H) is formed, and... 

Treatment of 2- or 4-(p-formylphenyl)-2/f-l,2,3-triazoles with p-tolyl-substituted heterocycles such as benzo[6]furans,58,63 benzol-thiophenes,56,63 benzoxazoles,63,64 benzisoxazoles,54 oxazoles,63 isoxa-zoles,63 oxadiazoles,63,65 benzotriazoles,63 and y-triazolo [ 1,5-a]-pyri-dines19 has led to the formation of a number of new stilbene derivatives some of which are shown in Table XI. 

Isomerization of benzo[/]-l,5-diazabicyclo[3,2,2]nonene in 8.8 N HBr at 140°C yielded l,2,3,5,6,7-hexahydropyrido[l,2,3-de]quinoxaline (83 KGS677). Photolysis of dimethyl l-(quinolin-8-yl)-l,2,3-triazole-4,5-di-carboxylates in MeCN resulted in stable an/tydro-2,3-dimethoxycarbonyl-3//-pyrido[l,2,3-de]quinoxalin-4-ium hydroxides [87JCS(P1)403]. 6-Hy-droxymethyl-2-methyl-7-methoxy-l,2,3,4-tetrahydro-6//-pyrazino-[1,2-h]isoquinolin-4-one (138) was prepared from 5- [A-methyl-Ar-(ethoxy-... 

An investigation into the methylation of 37/-[l]benzothieno[2,3-J]-l,2,3-triazole (10) demonstrated that the combination of Me2S04 and the silver salt of (10) gives reasonable yields of 3-methyl-[l]benzothieno[2,3-benzo-thieno[2,3-. 

Nitrobenzotriazole was obtained by reduction of benzo-l,2,3,4-tetrazine 1,3-dioxides (BTDOs) with Na2S204 or SnCl2 via intermediate /V-nitrosobenzo-triazoles (Scheme 2.139) [162],... 

---