L,2,4-Triazol-3-ones

H- Pyrro lo[l,2-c][l,2,4]triazol-3-ones synthesis, 6, 991 Pyrroloyl azides Curtius rearrangement, 4, 288 Pyrrolyl anions acylation, 4, 232 alkylation, 4, 235 solvent effects, 4, 236 C-alkylation... 

CN 4-[4-[4-[4-[[2-(2,4-dichlorophenyl)-2-( 1H-1,2,4-triazol-1 -ylmethyl)-1,3-dioxolan-4-yl]methoxy]phenyl]-l-piperazinyl]phenyl]-2,4-dihydro-2-(l-methylpropyl)-3//-l,2,4-triazol-3-one... 

CN 2-[3-[4-(3-chlorophenyl)-l-piperazinyl]propyl]-5-ethyl-2,4-dihydro-4-(2-phenoxyethyl)-3f/-l,2,4-triazol-3-one hydrochloride... 

Similarly, the structure of 5-nitro-2,4-dihydro-377-l,2,4-triazol-3-one (NTO) 6 has been scrutinized using molecular orbital calculations using the 6-31+G and 6-311+G basis sets. These calculations examined the various tautomers of NTO and give an insight into the molecular mechanisms involved in its explosive decomposition <1996JA8048>. 

Semicarbazones 2 were converted into their corresponding mono-, di- and trisubstituted 2,4-dihydro-l,2,4-triazol-3-ones 3 (Scheme 3 1986JHC881). 

Thiosemicarbazone 4 reacted in a similar manner to give l,2,4-triazole-3-one 5 in good yield (1986JHC881), whereas at lower temperature (40 °C), unexpectedly, 2-methylamino-5-phenyl-l,3,4-thiadiazole 6 was isolated in low yield (Scheme 4). 

The endoxytriazolines originally described by Busch were later formulated either as meso-ionic l,2,4-triazol-3-ones (200) or as meso-ionic l,3,4-oxadiazol-2-imines (153). This ambiguity has now been... 

The meso-ionic l,2,4-triazol-3-ones (200) are stable to acid, but alkaline hydrolysis gives 1,4-disubstituted semicarbazides. They do not normally participate in 1,3-dipolar cycloadditions, but the meso-ionic 1,4-diphenyl-l,2,4-triazol-3-one (200, R = R = Ph, R = H) and benzyne yielded 2-phenylindazole. 1,2,4-Triazolium salts (211) are formed with triethyloxonium tetrafluoroborate. Reduction of the meso-ionic compound 200, R = Me, R = R = Ph, with lithium aluminum hydride gives the triazolidinone 212. ... 

The suggestion that three-membered heterocycles (362) are involved is illustrated by the postulated generation of derivatives of IH-diazirine (315 and 345), thiiren (328), thiazirin (337), and lif-triazirine (358). These three-membered heterocycles belong to the class of 4n-antiaromatic heterocycles their possible role as reaction intermediates is of general interest. There is, however, an interesting difference between the photochemistry of sydnones (Fig. 4) and meso-ionic l,2,4-triazol-3-ones (Fig. 6). In both cases IH- azirines (315 and... 

NTO [5-nitro-l,2,4-triazole-3-one (C2H2N403)] (2.18) is a new energetic material with attractive characteristics and high performance. It has a high heat of reaction and is less sensitive and more stable than RDX. 

The reaction of unsymmetrically substituted 1,3-diketones such as 5-acetoacetyl-6-methoxy-2,3-diphenylbenzofuran or its 6-acetoacetyl-5-methoxy isomer with 5-amino-2-phenyl-l,2,4-triazol-3-one (72) could produce 74 and/or 76. However, a single product was obtained which was assigned the structure 74 on the basis of spectral properties (88PJS334) (Scheme 32). 

R = Me). This yields a mixture including the meso-ionic compound 200, R1 = R2 = Me, R3 = Ph. The 1,3-dipolar cycloaddition of phenyl isocyanate to JV-phenylsydnone (205) yielding the meso-ionic 1,4-diphenyl-l,2,4-triazol-3-one (200, R1 = R3 = Ph, R2 = H)137,13> provides a comparatively rare example of the interconversion of one type of meso-ionic compound into another. 

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