Tetrazolyl radicals

Oxidation of azole anions can give neutral azole radicals which could, in principle, be tt (139) or a- (140) in nature. ESR spectra indicate structure (141 hyperfine splittings in G) for imidazolyl radicals, but both tt- and cr-character have been observed for pyrazolyl radicals. Tetrazolyl radicals (142 4 143) are also well known (79AHC(25)205). Oxidation of 2,4,5-triarylimidazole anions with bromine gives l,l -diimidazolyls (144) which are in equilibrium with the dissociated free radical (145) (70AHQ 12)103). 

Tetrazolo[5,1 -6][ 1,2,4]triazin-3-ones synthesis, 3, 392 Tetrazolyl radicals oxidation, 5, 60 Tetrazolyl ylides structure, 5, 793 Tetrenolin occurrence, 4, 706 Tetrodotoxin... 

As is the case with the Wittig and Peterson olefinations, there is more than one point at which the stereoselectivity of the reaction can be determined, depending on the details of the mechanism. Adduct formation can be product determining or reversible. Furthermore, in the reductive mechanism, there is the potential for stereorandomization if radical intermediates are involved. As a result, there is a degree of variability in the stereoselectivity. Fortunately, the modified version using tetrazolyl sulfones usually gives a predominance of the E-isomer. 

Electrochemical methods have been used extensively to elucidate the mechanism of reduction of tetrazolium salts. In aprotic media, the first step is a reversible one-electron reduction to the radical 154 as confirmed by ESR spectroscopy.256,266 As shown in Scheme 26, this radical can then disproportionate to the tetrazolium salt and the formazan anion (166) or take up another electron to the formazan dianion (167). The formation of the dianion through a direct reduction or through the intermediate tetrazolyl anion (168) has also been proposed.272-28 1,294 In aqueous solutions, where protonation/deprotonation equilibria contribute to the complexity of the reduction process, the reduction potentials are pH dependent and a one-electron wave is seldom observed. 

Pentachloropyridine undergoes a regio-selective dechlorination to give 2,3,5,6-tetrachloropyridine [118]. The reduction of 1- and 2-phenoxynaphthalene at the cathode or by an alkali metal afforded phenol and naphthalene. The intermediacy of the naphthalene radical has been made probable by the use of an internal radical trap [119]. 5-Aryloxy-l-phenyltetrazoles cleave reductively predominantly at the tetrazolyl-O bond. The relative rates of... 

If we adopt Roman numerals for tetrazene , then the name will be (Tetrazolyl-5 ), guanyl.l, IV-tetrazene orGuanyl(tetrazolyl-5f). IV, 1-tetrazene. The figure 5 which follows the name of the tetrazoly radical, signifies that the position 5 of the tetrazolyl is connected to the tetrazene. 

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