Subject triazole

Nucleotides containing the nucleobases T, G, and C are also subject to conversion in an analogous way. In place of CDI, caibonyldibenzimidazole, carbonyldi-1,2,4-triazole, and carbonyldibenzotriazole were utilized in these reactions. 

Tetranitro derivative 90 (z-TACOT Section 12.10.15.5) treated with methanolic sodium methoxide at ambient temperature does not lead to simple product of nucleophilic substitution of a nitro group but provides compound 92. Its formation can be rationalized by introduction of the methoxy group into the 1-position, followed by scission of the remote triazole ring of 91 to give the final product. Compound 90 subjected to the vicarious nucleophilic substitution (VNS) conditions using either hydroxylamine or trimethylhydrazinium iodide gives a very insoluble red solid, which was identified as l,3,7,9-tetraamino-2,4,8,10-tetranitrobenzotriazolo[2,l- ]benzotriazole 93 (Scheme 5) <1998JOC3352>. 

The photoelimination of carbon dioxide from esters and lactones is a process that has been the subject of detailed investigations. Discussion here is limited to nitrogen containing systems. 3,4-Diphenylsydnone (464), on irradiation in benzene, is converted via the nitrile imine 465 into 2,4,5-triphenyl-1,2,3-triazole (466)388 initial bond formation between N-2 and C-4 followed by loss of carbon dioxide to give the diazirine 467 is proposed to account for the formation of the nitrile imine. Nitrile imines generated in this way have been trapped with alkenes and alkynes to give pyrazoles389... 

Azide 367 is prepared from 4-r -butyl-2-nitroaniline in 76% yield by its diazotization followed by treatment with sodium azide. In a 1,3-dipolar cycloaddition with cyanoacetamide, azide 367 is converted to triazole 368 that without separation is directly subjected to Dimroth rearrangement to give derivative 369 in 46% yield. Reduction of the nitro group provides ortfc-phenylenediamine 371 in 91% yield <2000EJM715>. Cyclocondensation of diamine 371 with phosgene furnishes benzimidazol-2-one 370 in 39% yield, whereas its reaction with sodium nitrite in 18% HC1 leads to benzotriazole derivative 372, which is isolated in 66% yield (Scheme 59). Products 370 and 372 exhibit potassium channel activating ability <2001FA841>. 

Arylazo-4-(3-ethoxycarbonylureido)furoxans 62, which were synthesized by the reactions of 4-amino-3-arylazo-furoxans with ethoxycarbonyl isocyanate, were subjected to cascade rearrangements under the action of potassium r/-butoxidc in dimethylformamide or by heating in dimethyl sulfoxide to form 4-amino-2-aryl-5-nitro-2//-l,2,3-triazoles 63 (Scheme 13) <2001MC230, 2003RCB1829>. 

Tomas et al. [281] have calculated the tautomeric equilibrium of 1,2,3-benzotriazole in the gas phase and compared their results to experimental data [282] derived from ultraviolet spectroscopy. Experiment suggests that 35 is about 4 kcal/mol more stable than 34 this result is consistent with calculations [281] at the MP2/6-31G level, which predict 35 to be 2.5 kcal/mol more stable than 34. The same level of theory predicts 33 to be 5.0 kcal/mol more stable than 32 in the parent triazole system. Although experimental data are available indicating 35 to be the dominant tautomer in CDCf and d6-dimethyl sulfoxide solutions [279, 283], this equilibrium does not appear to have been the subject of any modeling, continuum or otherwise. It may prove to be somewhat challenging, however. Tomas et al. point out that correlation effects favor 35 by about 5 kcal/mol at the MP2 level AMI, PM3, and HF calculations with moderate basis sets all predict... 

The reaction of 2-amino-guanidine-1 -acetic acid hydroiodide 331 with carbon disulfide, heating the substrates in DMF at 130-140 °C for 12 h, produces compound 332 in 76% yield. This compound was subjected to cyclization reaction with acetic anhydride to give 6,7-dihydro-5-oxo-imidazo[2,l-f][l,2,4]triazole 102 in 76% yield (Scheme 32) <1998MI1>. 

Basic hydrolysis of the [l,2,4]triazolo[5,l-3][l,3]thiazine derivative 77 was described to yield triazole-thione 78, the reaction proceeding in 59% yield <2005ZOR1092>. Related partially saturated triazolothiazines 79 were also subjected to ring-opening reaction aqueous hydrolysis afforded the acid 80 <2004KGS1256>, whereas reaction of 79 with hydrazine hydrate yielded the acid hydrazine 81 <2004ZOR260>. Both transformations took place in high yields. 

Fathalla et al. reported that some [l,2,4]triazolo[4,3- ]quinazoles can be subjected to various transformations involving the triazole nitrogen atom <2000MOL1210>. Thus, treatment of 186 with formaldehyde and pyrrolidine... 

Nagai et al. carried out various transformations with camphor-fused amino[l,2,4]triazine 191 <1998JHC293> (Scheme 39). Reaction of 191 with chlorocarbonylsulfenyl chloride yielded the fused thiadiazolone 192 in high yield (83%). The same starting compound also proved to be suitable for the synthesis of the fused triazole derivative 193. To this end, 191 was first subjected to two subsequent transformations first by dimethylformamide dimethylacetal followed by treatment with hydroxylamine hydrochloride to give an Ar-hydroxyamidine 193 in 90% overall yield, and then this compound was treated with polyphosphoric acid to yield the fused triazole product 194 in 92% yield. 

Photolytic. When triadimefon was subjected to UV light for 1 wk, p-chlorophenol, 4-chloro-phenyl methyl carbamate, and a 1,2,4-triazole formed as products (Clark et al., 1978). 

The nitrogen atoms of heterocycles like imidazoles and triazoles have been converted into IV-nitroimide groups. The A -nitroimide (164) is synthesized from 1-amino-1,3,4-triazole (162) by IV-amination of the tertiary nitrogen with 0-picrylhydroxylamine, addition of nitric acid to give the nitrate salt (163), followed by IV-nitration with nitronium tetrafluoroborate in acetonitrile. The 1,2,3-triazole (165) and the imidazole (166) ° are synthesized in a similar way. The synthesis of IV-nitroimides has been the subject of an excellent review. ... 

The synthesis of the 1,2,3-triazole ring has been the subject of many reviews, and is very well documented in CHEC-I. Developments since 1984 will be discussed using the same system as was employed in CHEC-I. For a general description and early work, see <84CHEC-i(5)705>. 

Only those compounds which do not have tautomeric aromatic triazole structures will be considered here, the others having been treated as triazoles. The triazolines are unstable and have been subjected to little study. Compounds which are disubstituted at the C(3) or C(5) atom are more stable than the mono- or unsubstituted analogues. The equilibrium has been observed by NMR spectroscopy between the six-membered tetrazine (75) and the triazolinethione (76) via the open-chain form, thus mirroring monosaccharide equilibria (Scheme 12) <90TL3927>. 

The photochemistry of iVC-diphenylsydnone (1, R = R = Ph) has been the subject of almost simultaneous study by a number of groups. " Some variations of isolated reaction products occurred, but the formation of 2,4,5-triphenyl-l,2,3-triazole (320, R = R = Ph)... 

As with the 1,2,3-isomers, 1,2,4-triazoles can also be halogenated on N-l to form reasonably stable products that are then subject to thermal... 

An extensive review of the chemistry of aliphatic and aromatic azides is given by Boyer and Canter [167] and Gray [168]. Organic azides are subject to various reactions such as the Bergmann degradation and the synthesis of peptides, the well known Curtius rearrangement, the Darapsky synthesis of a-aminoacids [169], for synthesis of triazoles [170], tetrazoles ( Schmidt reaction ) [169] and [171] etc. These reactions lie beyond the scope of the present book. 

This review covers the literature in primary journals to early 1981 and in Chemical Abstract Subject Indexes to Volume 94. The names used are those adopted by Chemical Abstracts, and the numbering system is [1,2,3) etc. for triazoles rather than the v- or s- symbols. 

Both ring positions and lateral positions - both at C4 and C5 - are activated by the O-silylation. Substituents can be introduced at the lateral 5-position by O-silylation followed by abstraction of the activated lateral proton with a weak non-nucleophilic base. The neutral species 428 formed is subject to nucleophilic allylic displacement of the silyloxy anion rendering laterally substituted triazole 429 in one pot (Scheme 121). 

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