Nitro-substituted triazoles, synthesis

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... 

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). 

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 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). 

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). 

Bis(hydroxymethyl)phosphonic acid esters that incorporated thymine were employed as a backbone to prepare short oligonucleotide chains. This chain was prepared by condensation of the bis(4,4 -dimethoxytrityl) protected phosphonic acid and iV or N -(2-hydroxyethyl)thymine in the presence of l-(2-mesitylenesul-fonyl)-3-nitro-l,2,4-triazole or by an Appel reaction with or N -(2-aminoethyl)thymine (89a-h). Selective removal of one DMT-group and phos-phitylation yielded the building blocks for solid supported synthesis of the short oligomers by the phosphoramidite approach. Holy has reported the synthesis of 8-amino and 8-substituted amino derivatives of acyclic purine nucleotide analogues. The 8-amino, 8-methylamino- and 8-dimethylamino-adenine and -guanine analogues of iV-(2-phosphonomethoxyethyl) and (S)-iV-(3-hydroxy-2-phosphono-methoxy-propyl) derivatives of purines (90a-i), were prepared by... 

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