Triazoles, nitro-, syntheses

Vilsmeier reaction, 4, 1051 Furo[3,2-6]pyrroles MO calculations, 6, 979 synthesis, 4, 1069 6, 1009 Furo[3,4-a]pyrrolo[2,1,5-cd]indolizine nomenclature, 1, 22 Furopyrylium salts, 4, 993-995 Furoquinolines biosynthesis, 4, 992 occurrence, 4, 988 pharmacology, 4, 992 reactions, 4, 988 synthesis, 4, 989 Furo[3,2-c]quinolines, 4, 991 Furo[3,4-fe]quinoxaline, 1,3-diphenyl-synthesis, 4, 993 Furoquinoxalines, 4, 992 Furo[2,3-6]quinoxalines synthesis, 4, 992 Furosemide toxicity, 1, 136 Furospinulosin UV spectra, 4, 587 Furospongin-I mass spectrometry, 4, 583 Furo[3,4-d][l,2,3]triazole, 2,6-dihydro-synthesis, 6, 996 Furo[3,4 -d][ 1,2,3]triazoles synthesis, 6, 996 Furoxan, 4-amino-3-aryl-tautomerism, 6, 404 Furoxan, 4-amino-3-methyl-synthesis, 4, 414 Furoxan, 4-aryl-3-methyl-rearrangement, 6, 408 Furoxan, 3-aryl-4-nitro-synthesis, 6, 414 Furoxan, 4-benzoyl-3-methyl-oxime... 

Process development of the synthesis of iodoaniline 28 began with an improved synthesis of l-(4 -aminobenzyl)-l,2,4-triazole (6) (Scheme 4.7), which was prepared in the medicinal chemistry synthesis, albeit with poor regioselectivity (Scheme 4.1). We found that this aniline intermediate 6 could be readily prepared in three steps in >90% overall yield from 4-amino-l,2,4-triazole (30) and 4-nitrobenzyl bromide (4) based on a modified literature procedure [9]. The condensation of 30 and 4 in isopropyl alcohol followed by deamination gave the nitro... 

Triisopropylbenzenesulfonyl)-3-nitro-1,2,4-triazole in the presence of 4-rtiorpholine pyridine-1-oxide was used with advantage as a coupling reagent for a solid-phase (p-alkoxybenzyl ester type resin) synthesis of peptides such as Leu-AIa-Gly-Val-OH or Leu-enkephalinamide (Tyr-Gly-Gly-Phe-Leu-NHs). The overall yield in the latter case was 70%, the purity of the peptide was 85-90%, and racemization was virtually zero.[38]... 

Synthesis of the amino-triazole derivative (43) was performed in the authors laboratory by Pati et al. [52] (Scheme 7). Substituted benzyl bromide was reacted with triphenylphosphine to produce the phosphonium bromide starting material, 44. The Wittig reagent, obtained by treatment with sodium hydride, was reacted with 3,4,5-trimethoxybenzaldehyde 18 to generate the nitro-stilbene 45 in good yields. The alkyne 46 was obtained by bromination of the stilbene, followed by didehydrobromination. Compound 46 was then reacted under thermal conditions with benzyl azides... 

Laval and Vignane reported the synthesis of the nitrotriazole (124) from the reaction of 3-nitro-1,2,4-triazole with 3,5-diamino-l-chloro-2,4,6-trinitrobenzene. The nitrotriazole (124) is a useful secondary high explosive, exhibiting high performance and a low sensitivity to impact. 

Gilardi and co-workers reported a synthesis of 4-(trimethylsilyl)-5-nitro-1,2,3-triazole (136) via a cycloaddition between l-nitro-2-(trimethylsilyl)acetylene (134) and trimethylsilyl azide (135). This may provide a route to 4,5-dinitro-l,2,3-triazole via nitrodesilylation or lead to the synthesis of 4-amino-5-nitro-l,2,3-triazole, an isomer of ANTA. 

The starting material for the synthesis of the 4-substituted derivatives 176 was the tautomeric 4(7)-nitrobenzo-triazole 173, which upon methylation with dimethyl sulfate in aq NaOH afforded the 4-nitro-2-methylbenzotriazole 174. The H NMR spectrum of the purified reaction mtKture after methylation showed the existence of all three triazole ring iV-methylated isomers in equal amounts. Compound 174 was isolated by virtue of its insolubility in cone HCl. Purity of products was confirmed by gas liquid chromatography (GLC). 

Nitro-l,2,4-triazol-5-one (NTO) [Structure (2.49)] or oxynitrotriazole (ONTA)has been reported as another IHE coupled with better performance [152-157]. Almost all aspects of NTO-synthesis, structural aspects, chemical and explosive properties including thermal behavior have been investigated [158-161]. NTO exists in two polymorphic forms, that is, -form and P-form. It has been established that a-NTO is the stable and dominating form whereas P-NTO is only found in the product on recrystallization of NTO from a methanol or ethanol/methylene chloride mixture [162]. French researchers have recently reported its evaluation as an explosive for warhead filling without a binder and also as a PBX [155]. Further, synthesis of NTO is easy consisting of only two steps (Scheme 2.9) and uses inexpensive starting materials. 

Scheme 2.10 Synthesis of 5-nitro-4,6-bis(5-amino-3-nitro-l H-l, 2,4-triazole-l -yl) pyri m id i ne (DANT N P).

The most widespread method of introducing nitro group in aromatic compounds, i.e., electrophilic substitution, is mainly used for the preparation of nitrodiazoles and benzazoles. The accumulation of pyridine nitrogen atoms in the cycle reduces the electrophilic substitution ability of compounds. Therefore, some indirect methods of introducing the nitro group are employed for the synthesis of triazole and tetrazole nitro derivatives. 

The convenient method of 3 -nitro-5-cloto-1,2,4-triazole synthesis from corresponding 3-aminoderivative [447] was worked out. The aforementioned way [348] is very laborious and dangerous (Scheme 58). 

The construction of a heterocyclic ring from two reagents, one of which contains a nitro group, is widely used in the synthesis of the nitro derivatives of pyrazole, isoxazole, and 1,2,3-triazole. Thus, for example, the reaction of sodionitromalonal-dehyde with substituted hydrazines leads to the corresponding derivatives of 4-nitropyrazole [33, 61, 471 173] (Scheme 63). 

The reaction of sodium azide with l-bromo-l-nitro-2-arylethenes takes place by a formal 1,3-cycloaddition Scheme leading to 4(5)-aryl-5(4)-nitro-l,2,3-triazoles [487-489], During the synthesis of nitrotriazoles the bromonitroarylethenes can be replaced successfully by the more readily obtainable l,2-dibromo-l-nitro-2-arylethanes [489], The intermediate product in the synthesis of 3-nitropyrazoles from 2,2-dinitroethanol and diazo ketones or diazoacetic ester is 1,1-dinitroethene [490,491] (Scheme 68). 

A convenient preparative method for the synthesis of 2-substituted 4-nitro-l,2,3-triazoles is based on the condensation of diazonium salts with metazonic acid. The latter is in turn synthesized by the action of alkali on nitromethane [423,508-510] (Scheme 78). 

Step 3 Synthesis of 5-nitro-2(3,5-diamino-2,4,6-trinitrophenyl)-l,2,4-triazole. 

Reese CB, Ubasawa A. Namre of side-reactions in oligonucleotide synthesis involving arenesulphonyl derivatives of 3-nitro-1,2,4-triazole and related condensing agents. Nucleic Acids Symp. Ser. 1980 (7) 5-21. 

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