Oxatriazol-5-ones

4-Oxatriazol-5-ones Anhydro-5-hydroxy-l,2,3,4-oxatriazolium Hydroxides) (271) 

Analogous routes cannot be successfully employed for the synthesis of meso-ionic 3-aryl-1,2,3,4-oxatriazol-5-ones (271). Thus, nitrosation of 1-arylsemicarbazides yields arylazocarbonamides with loss of nitroxyl.186 Meso-ionic 3-aryl-1,2,3,4-oxatriazol-5-ones are formed by 

Information concerning the chemistry of meso-ionic 3-alkyl- and 3-aryl-l,2,3,4-oxatriazol-5-ones (271) is limited, but further investigation may well be encouraged by reports of pronounced hypotensive activity.192 3-Cyclohexyl-1,2,3,4-oxatriazol-5-one (271, R = cyclohexyl) is resistant to attack by dilute mineral acid, but warm concentrated sulfuric acid gives cyclohexanol and carbon dioxide.184 In contrast, acid hydrolysis of 3-phenyl-1,2,3,4-oxatriazol-5-one (271, R = Ph) yields phenyl azide.189 Meso-ionic 3-cyclohexyl-l,2,3,4-oxatriazol-5-one shows two unusual reactions its photoirradiation in benzene gives cyclohexanone97 and heating with diphenylacetylene yields l-cyclohexyl-4,5-dipheny 1-1,2,3-triazole (276)104 rather than the expected 2-cyclohexyl-4,5-diphenyl-1,2,3-tri azole. 

The dipole moment of the A-phenyl derivative (271, R = Ph) in benzene solution is 6.14 D,108 which may be compared with the molecular orbital calculations by Sundaram and Purcell193 which give a value of 5.3 D for the meso-ionic l,2,3,4-oxatriazol-5-one heterocyclic ring moment. 

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CN3O 0 N N N Mesoionic 3-phenyl-l,2,3,4-oxatriazole-5-phenylimine mesoionic 3-phenyl-l,2,3,4-oxatriazol-5-one... 

The mesoionic compounds can be named in several ways. The systematic name for structure (4) is a 3-substituted anhydro-5-hydroxy-l,2,3,4-oxatriazolium hydroxide. Similarly, structure (5) is named a 3-substituted anhydro-5-thiolo-l,2,3,4-oxatriazolium hydroxide, and structure (6) a 3-substituted anhydro-5-amino-l,2,3,4-oxatriazolium hydroxide. Frequently used names for structure (4) are 3-substituted 5-hydroxy-1,2,3,4-oxatriazolium hydroxide inner salt Chemical Abstracts), 3-substituted l,2,3,4-oxatriazol-5-ylio oxide, or 3-substituted l,2,3,4-oxathiazolylium-5-olate. For practical purposes, the term mesoionic l,2,3,4-oxatriazol-5-one is often used. Analogously, (5) and (6) are named mesoionic l,2,3,4-oxatriazol-5-thione and mesoionic l,2,3,4-oxatriazol-5-imine, respectively. 

Meso-ionic 3-alkyl-l,2,3,4-oxatriazol-5-ones (271) are obtained by the nitrosation of 1-alkyl semicarbazides, RNHNHCONHj. At low temperatures, the intermediate A-nitroso derivatives (272) can be isolated, which cyclize on heating. An alternative synthetic route is illustrated by the formation of meso-ionic 3-methyl-l,2,3,4-oxatriazol-5-one (271, R = Me) from A-nitroso-iV-methylhydrazine (273) and phosgene. ... 

Heterocycle (85) may be systematically described as 3-substituted anhydro-5-hydroxy-1,2,3,4-oxatriazolium hydroxide. However, this nomenclature is somewhat cumbersome and the terminology mesoionic has been used throughout this review. Thus compounds (85)-(87) and (91) are named mesoionic l,2,3,4-oxatriazol-5-ones (85), -5-thiones (86), -5-imines (87) and mesoionic l,2,3,4-thiatriazole-5-alkenes (91), respectively. Using IUPAC Rule. C-87 (85) is named 3-substituted l,2,3,4-oxatriazol-5-ylio oxide or 3-substituted l,2,3,4-oxathiazolylium-5-olate and (87 R = R1 = Ph) is named iV-[3-phenyl-5-(l,2,3,4-oxatriazolio)]anilide. 

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