Tetrazol-5-ones

4-Tetrazol-5-ones (A nhydro-5-hydroxy-1,2,3,4-tetrazolium Hydroxides) (392) 

Meso-ionic l,2,3,4-tetrazol-5-ones (392) have been known for many years, although they were not initially recognized as having betaine-type structures. Treatment of l,5-diphenyl-3-nitroformazan (393, X = NOj) 

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Tefrazolo[2,3-e]isoxazole, 2-methyl-IR spectra, 6, 978 Tetrazol-5-one, 1-aryl-acylation, 5, 821 Tetrazol-5-one, 1,4-dimethyl-2-oxides synthesis, 3, 533... 

A mixture of 22 parts of 1 -ethyl-1,4-dihydro-5H-tetrazol-5-one,45 parts of 1 -bromo-2-chloro-ethane,26 parts of sodium carbonate,0.3 part of potassium iodide and 240 partsof 4-methyl-2 pentanone is stirred and refluxed overnight with water-separator. The reaction mixture is cooled, water is added and the layers are separated. The aqueous phase is extracted three times with dichloromethane. The combined organic phases are dried, filtered and evaporated. The residue is purified by column-chromatography over silica gel using trichloromethane as eluent. The pure fractions are collected and the eluent is evaporated, yielding 28.4 parts (80%) of 1-(2-chloroethyi)-4-ethyl-1,4-dihydro-5H-tetrazol-5-one as a residue. 

CijHijNjOi 95885-13-5) see Nefazodone hydrochloride l-ethyl-l,4-dihydro-5f/-tetrazol-5-one (C,H4N40 69048-98-2) see Alfentanil ethyldiisopropylamine... 

In the early investigation of the nitrosation of 1,4-diphenyl-thiosemicarbazide (279, R = R = Ph), the product was obtained as deep red needles, m.p. 110°, and was allocated the remarkable 1,3-endoxyhydrazomethylene structure (280). Treatment of this deep red compound with warm aqueous alkali gave a colorless isomer, m.p. 157°, which was formulated as having one of the equally unacceptable structures 281 or 282. Recent investigations have established that nitrosation of 1,4-diarylthiosemicarbazides (279) yield the meso-ionic 1,2,3,4-oxatriazol-5-imines (277), which are transformed by base into the meso-ionic isomers (278). These alkaline transformation products formulated as meso-ionic l,2,3,4-tetrazol-5-ones (278) are in fact identical (see Section VII, J, 1) with substances prepared, but not formulated, by von Pechmann many years ago. ... 

Mixtures of meso-ionic l,3-diaryl-l,2,3,4-tetrazol-5-ones (289) and... 

Methyl-5-hydroxytetrazole (292) and diazomethane yield 2-methyl-S-methoxytetrazole and an isomer which could be meso-ionic 1,3-dimethyl-l,2,3,4-tetrazol-5-one (289, R = = Me). Treat-... 

Synthesis The cyclization of ethyl isocyanate with sodium azide by means of AICI3 in refluxing THF gives 1 -ethyl-1,4-dihydro-5H-tetrazol-5-one, which is alkylated with 1-chloro-2-bromo-ethane in the presence of Na2CC>3 and Kl in refluxing 4-methyl-2-pentanone to afford 1-ethyl-4-(2-chloroethyl)1,4-dihydro-5H-tetrazol-5-one i (Janssen (Janssen), 1978 Janssens et al., 1986 Hopkins, 1981 Kleemann et al., 1999). 

Scheme 1 Synthesis of 1-ethyl-4-(2-chloroethyl)-1,4-dihydro-5H-tetrazol-5-one.

Janssens, F., Torremans, J., Janssen, P.A.J. Synthetic 1,4-disubstituted 1,4-dihydro-5H-tetrazol-5-one derivatives offentanyl alfentanil (R 39209), a potent, extremely short-acting narcotic analgesic, J. Med. Chem. 1986, 29, 2290-2297. 

Typical 1,3-dipolar cycloreversion is found for the decomposition of alkyl-substituted 2-tetrazolines (43) (88CB1213), l,4-dihydro-l,2,3,4-tetrazol-5-ones (44), and -thiones (45) (97JHC113). For these reactions two paths are possible that can be distinguished when the substituents on N-l and N-4 are different. For 2-tetrazolines ring contraction leading to diaziridines is also possible (discussed earlier). Cycloreversion of 43 yields imines and azides (88CB1213). 

Meso-ionic l,2,3,4-tetrazol-5-ones (289) react with triethyloxonium tetrafluoroborate, yielding salts (294)197 that react with sodium sulfide in dimethylformamide, giving meso-ionic l,2,3,4-tetrazole-5-thiones (295).207... 

Acidities of tetrazol-5-ones (thiones) 11, 65, 143, and 164 are in the same range as the acidities of NH-tetrazoles, although in these compounds dissociation occurs not at the OH or SH groups but at the nonaromatic 1,4-dihydro-tetrazole ring (Equation 13) <2006RJ01585>. 

Gas-phase thermolysis of substituted tetrazoles (46a,b and 48), the 1,4-disubstituted 1,4-dihydro-5//-tetrazol-5-ones (49a-f) and the 1,4-disubstituted 1,4-dihydro-5/7-tetrazol-5-thiones (50b,c,e-h) have been monitored by photoelectron spectroscopy. ... 

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