Tetrazoles azido

Anilino tetrazole, Azido-, C7HgNg and Diazido-C7HsNn Derivatives were not found in Beil or CA through 1956... 

Other tetrazole-azido-heteroaromatic equilibria have been studied where the heterocyclics to which the azide group is attached (or to which it is condensed as a tetrazole ring) are 1,2,3-triazoles, pyrimidines quinoxalines , naphthothiazoles , 1,3,5-tria-... 

Action of HSO3CI on 2-substituted thiazoles affords the 5-chlorosulfonyl derivatives (337, 338). Addition of 6-phenylthiazolo[2,3-e]tetra2ole to oleum opens the tetrazole ring to form 2-azido-4-phenyI-thiazolyl-5-sulfonic acid, isolated as its salt (339). 5-Chloro-sulphonyl derivative is obtained similarly by action of HSO,Cl. 

The azido/tetrazole rearrangement of pyrazole and indazole derivatives will be discussed in the corresponding section (4.04.2.3.4(v)). 

Azidopyrazoles (455) exist as such even when the azido group is at the 3-position where an azido-tetrazole equilibrium is possible (469) (470) (77AHC(2l)72, 78AHC(22)184). 

Azido hydroxy tetrazole (mercury and silver salts)... 

C. Ligands Susceptible to Ring-Chain and Azido-Tetrazole Tautomerism. 294... 

Valence tautomerism of heterocyclic systems containing tetrazole rings has received much attention [76AHC(S1), p. 498 84CHEC-I(5)791 96CHEC-1I(4)621], The latest contributions to this area are considered in Section IV,C, which is concerned with the topic of azido-tetrazole tautomerism. 

This conclusion was largely confirmed at the much higher (MP2/6-311G ) level of approximation for the case of interconversion of azido-azomethine and tetrazole forms of thiazole[3,2-d]tetrazole 312 (Scheme 118) (98JA4723). 

The azido-3(5)-phenyl-4-pyrazole isomer 317 is the sole form in the solid state by X-ray study (74CSC713).The azidoazole isomers also predominate in the ease of 3(5)-azido-s-triazoles 318, 4(5)-azido-v-triazoles 319, azido-tetrazole 320 [77MI545, 86JCS(CC)959], and azidoisoxazoles 321 (77CJC 1728,77JHC1299). 

In contrast to the 2,4-diazidopyrimidines, only one azido group is involved in ring-chain transformations of 4,6-diazidopyrimidine 342 (Scheme 134) (88DOK115).The content of the tetrazole tautomer 342AT increases... 

Azido-tetrazole isomerism was briefly mentioned in the previous survey on tautomerism (76AHCSl,p. 547) and systematically dealt with in the reviews on tetrazoles by Butler [77AHC(21)324] and on aromatic azapenta-lenes by Elguero et al. [78AHC(22)183]. We now discuss the data which was not previously surveyed. 

Preu et al. have reported that azido-tetrazole isomerism of azido-1,2,3-triazoles 131A to the intermediate bieyeles 131T is neeessary to aeeount for the formation of a-diazoalkylterazolides [98JCS(P2)785]. 

Studies of presumed azido-tetrazole tautomerism for 3-azido-l,2,4-benzotria-zine 1-oxides 3 show that compounds 3 exist only in the form of azides, both in the crystalline state and in solution. Similar results were obtained in the studies of 3-azido-1,2,4-triazine 1-oxides 4, which have never been detected in the tetrazole form (69CB3818, 77JHC1221, 82JOC3886). 

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