Alkylation of 4(5)-nitro-1,2,3-triazole with alcohols in strongly acidic media

Alkylation of 4(5)-nitro-1,2,3-triazole with alcohols in concentrated H₂SO₄ occurs at all three endocyclic N atoms, giving a mixture of isomeric N(1)-, N(2)-, and N(3)-alkyl-4-nitro-1,2,3-triazoles (alkyl is isopropyl, sec-butyl, and cyclohexyl). The selectivity of the alkylation depends on the alcohol used. The most selective alkylation is provided at the N(2) atom when isopropyl (81%) and sec-butyl alcohols are used (67%). With an increase in the reaction time, also in the order isopropyl-, sec-butyl-, and cyclohexyl-4-nitro-1,2,3-triazoles, the N(2)-isomers undergo isomerization into N(1)-alkyl-4-nitro-1,2,3-triazoles. In all the cases, the fraction of the N(3)-substitution products in the mixtures is 6–30%.     

Acidic N-dealkylation in nitrotriazolium salts

New selective synthesis of 1-alkyl-5-nitro-1,2,3-triazoles and 1-alkyl-4-nitro-1,2,3-triazoles has been developed, involving acid N-dealkylation of the relative 4-nitro-1,2,3- and 3-nitro- 5-R-1,2,4-triazolium salts. The assortment of novel 1-alkyl- 4(5)-nitro-1,2,3-triazoles has been thus essentially expanded. Treatment of relative 3-nitro-1,2,4-triazolium salts with HCl or HBr proceeds mostly as S_N^ipso-substitution of the nitro group.     

Quantum-chemical investigation of certain physicochemical properties of C-nitro-1,2,3-triazole and N-alkyl-4(5)-nitro-1,2,3-triazoles

Quantum-chemical calculations have been carried out on molecular electrostatic potentials, proton affinity in the gas phase, gas phase basicity, and pK _BH+ values in aqueous solution for C-nitro- and N-alkyl-4(5)-nitro-1,2,3-triazoles, and the relative stability of the isomeric N-alkyl-4(5)-nitrotriazoles (alkyl = Me, Et, i-Pr, t-Bu) in the gas phase and in aqueous solution. For all the studied substances in the gas phase the 2H-tautomer and the N(2)-isomers were considerably more stable than the corresponding N(1) compounds, and the 3H-tautomer and N(3)-isomer were the least stable. In aqueous solution 1- and 3-isomers had close values of energies, but in the case of C-nitro-1,2,3-triazole the 1H form became even more stable than the 2H-form. It was established which ring nitrogen atoms of 1,2,3-triazoles are protonated in the gas phase and in solution. The obtained data correlate well with the results of experimental investigations on the alkylation of 1,2,3-triazoles in acidic and basic media and of the experimental investigation on the alkylation of C-nitro-1,2,3-triazoles with diethyl sulfate carried out in the present work. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1816–1828, December, 2008.     

N-Alkylation of 4-nitro-1,2,3-triazole revisited. Detection and characterization of the N3-ethylation product, 1-ethyl-5-nitro-1,2,3-triazole

The products of the alkylation of sodium 4-nitro-1,2,3-triazolate with ethyl bromide were investigated using ¹H, ¹³C, and ¹⁵N NMR spectroscopy. It was found that alkylation proceeds on the triazole nitrogen atoms giving a mixture of three isomeric N-ethyl-4-nitro-1,2,3-triazoles. The molar ratio of N1, N2, and N3-alkylation products was 4:8:1. The formation of a minor N3-isomer, namely 1-ethyl-5-nitro-1,2,3-triazole was confirmed by X-ray structural analysis of single crystals of its tetranuclear copper(II) complex obtained by reaction of copper(II) chloride dihydrate with a mixture of the N2 and N3-isomers.     

3-Nitro-1,2,4-triazol-5-one derivatives

3-Nitro-1,2,4-triazol-5-one and its monomethyl derivatives react with methyl vinyl ketone to give products of addition to the ring N₁ and N₄ atoms. The reaction with formaldehyde and N-methylolacetamide proceeds only at the N₁ atom. The keto derivatives of 3-nitro-1,2,4-triazol-5-one undergo the Schmidt reaction to give the corresponding acetamides. A number of compounds that include functional groups in the N₁-alkyl substituent of the 3-nitro ring were obtained by treatment of the bases of N₁-substituted 3,5-dinitro-1,2,4-triazoles in aprotic media.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 552–558, April, 1981.     

Cyclization of substituted 3,4-diaminopyridines into 1H-[1,2,3]triazolo[4,5-c]pyridine 2-oxide derivatives during the nitration process

The nitration of pyridine-3,4-diamine, its N,N′-diacetyl derivative, and N ⁴-alkylpyridine-3,4-diamines with excess nitric acid in concentrated sulfuric acid at 60°C was accompanied by cyclization with formation of the corresponding 1-substituted 4-nitro-1H-[1,2,3]triazolo[4,5-c]pyridine 2-oxides. 4-Chloro-1H-[1,2,3]triazolo[4,5-c]pyridine 2-oxide derivatives were obtained under analogous conditions from 2-chloropyridine-3,4-diamine, its N,N′-diacetyl derivative, and 2-chloro-N ⁴-methylpyridine-3,4-diamine. The nitration of these compounds at 80–90°C gave 4-chloro-7-nitro-1H-[1,2,3]triazolo[4,5-c]pyridine 2-oxides.     

Heterylation of 3-R1-5-R2-1,2,4-Triazoles with Derivatives of 3,5-Dinitro-1,2,4-Triazole

Heterylation of 3-R¹-5-R²-1'2'4-triazoles (pK _a 3-12) with N-alkyl-, N-alkenyl-, N-alkoxy-carbonyl-, N-oxoalkyl-, N-nitroxyalkyl, N-nitroaminoalkyl-3'5-dinitro-1'2'4-triazoles results insubstitution of a nitro group in 5 position of the dinitro compound yielding 1-R-methyl-3-nitro-5-(3-R¹-5-R²-1,2,4-triazolyl)-1,2,4-triazoles. The side processes: Hydroxide-ion attack on C⁵ and (or) N¹ of the ring both in the substrate and in the target compound afford 1-R-methyl3-nitro-1,2,4-triazol-5-ones, 3,5-dinitro-1,2,4-triazole and NH-acids of N-C-bitriazole series. Optimal reaction media are aprotic dipolar substances, and for compounds prone to heterolysis ethyl acetate-water systems. The azole pK _a is the decisive factor controlling the composition and the ratio of reaction products. The process is promising for azoles with pK _a > 5, and the optimal range of pK _a is 8-10.     

Synthesis of phthalan and phenethylamine derivatives via addition of alcohols to rhodium(II)-azavinyl carbenoids

1-Sulfonyl-1,2,3-triazoles undergo inter- and intramolecular 1,3-OH insertion with rhodium(II)-azavinyl carbenoid intermediates upon treatment with a rhodium(II) catalyst. Products of this transformation contain a synthetically versatile N-(2-alkoxyvinyl)sulfonamide, enabling divergent reactivity toward several N-protected phenethylamine derivatives under various conditions. Notably, products with a phthalan framework can be accessed directly from 4-aryl-1-sulfonyl-1,2,3-triazoles bearing a pendant alcohol.     

Trifluoromethyl Sulfones and Perfluoroalkanesulfonamides of the Azole Series

2-Phenyl-4-trifluoromethylsulfonylmethyl-2H-1,2,3-triazole was synthesized from 4-bromo-methyl-2-phenyl-2H-1,2,3-triazole and sodium trifluoromethanesulfinate CF₃SO₂Na. 1(2)-Ethyl-4-nitro-1(2)H-1,2,3-triazoles and 4-nitro-2-phenyl-2H-1,2,3-triazole were reduced to the corresponding amines. Intermediate 1,2-bis(1-ethyl-1H-1,2,3-triazol-4-yl)diazene 1-oxide exists as a mixture of syn and anti isomers, the former being stabilized via formation of a strong intramolecular hydrogen bond. The reduction of 2-ethyl-4-nitro-2H-1,2,3-triazole in the presence of HCl afforded the target 4-amino-2-ethyl-2H-1,2,3-triazole and also 4-amino-5-chloro-2-ethyl-2H-1,2,3-triazole. Treatment of alkyl-substituted 4-amino-1,2,3-triazoles with trifluoromethanesulfonyl chloride and pentafluoroethanesulfonyl chloride gave N-triazolyl-substituted trifluoromethane- and pentafluoroethanesulfonamides and -imides.     

Synthesis of 1,4,5-trisubstituted-1,2,3-triazoles by copper-catalyzed cycloaddition-coupling of azides and terminal alkynes

Primary, secondary, and aromatic azides undergo 1,3 dipolar cycloaddition-coupling with an excess of alkyne in the presence of Cu(CH₃CN)₄PF₆ as catalyst, N,N,N′-trimethylethylenediamine as ligand, molecular oxygen, and 4-methoxymorpholine N-oxide (NMO) as co-oxidant to afford 1,4,5-trisubstituted-1,2,3-triazoles.     

Reactions of 4-nitro-1,2,3-triazole with alkylating agents and compounds with activated multiple bonds

When 4-nitro-1,2,3-triazole is alkylated, a mixture of N₁- and N₂-isomers is formed, with the latter usually predominating. The same behavior is also observed in addition reactions of 4-nitrotriazole to activated multiple bonds.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 932–935, July, 1986.     

Aminomercuration intramoleculaire d'aziridines cycloocteniques et de leurs aminoalcools precurseurs

N-substituted cyclooctenic aziridines undergo intramolecular mercuration with mercuric salts; after reduction, N-substituted 9-azabicyclo[3.3.1]- and [4.2.1]nonanes are isolated. Mercuration of amino alcohols (precursors to aziridines) leads to the same products but with different yields dependent on the mercuric salt used. In some cases, aziridinium salts are intermediates in basic medium from the organo mercuric compounds during reduction. Extension of this reaction is studied with two aliphatic models.     

A facile synthesis of 3-substituted 2-cyanoquinazolin-4(3H)-ones and 3-alkyl-2-cyanothieno[3,2-d]pyrimidin-4(3H)-ones via 1,2,3-dithiazoles

The reaction of methyl anthranilate with 4,5-dichloro-1,2,3-dithiazolium chloride (Appel's salt) in the presence of pyridine (2 equivalents) in dichloromethane at room temperature gave methyl N-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)anthranilate ( 3a ) (50% yield), which reacted with sterically less hindered primary alkylamines to give directly 3-alkyl-2-cyanoquinazolin-4(3H)-ones 5 in moderate to good yields. With tert-butylamine, N-(2-methoxycarbonylphenyl)iminocyanomethyl N-(tert-butyl) disulfide 7 and methyl 2-(N-cyanothioformamido)anthranilate ( 8 ) were isolated in 33% and 59% yields, respectively. The cyano group of quinazoline 5a (R = CH₃) is readily displaced by various nucleophiles to give 2-substituted quinazolinones 11–19 , which indicates that compounds 5 can be utilized as starting materials for the synthesis of new 2-substituted quinazolines. Similarly 3-alkyl-2-cyanomieno[3,2,-d]pyrimidin-4(3H)-ones 22 were prepared from methyl 3-[N-(4-chloro-5H-1,2,3-dimiazol-5-ylidene)]-2-thiophencarboxylate ( 21 ) in moderate to good yields.     

A Theoretical Study on the Tautomerism of C-Carboxylic and Methoxycarbonyl Substituted Azoles

DFT calculations (B3LYP/6-31+G^**) have been carried out on 106 tautomers and conformers of NH-azoles bearing CO₂H and CO₂CH₃ groups. The following azoles systems have been studied: 2-substituted pyrroles, 2-substituted indoles, 2-substituted imidazoles, 2-substituted benzimidazoles, 4(5)-substituted imidazoles, 3(5)-substituted pyrazoles, 3-substituted indazoles (1H and 2H), 3,4(5)-substituted-1,2,3(5)-triazoles, 2,3(5)-substituted-1,2(3),4-triazoles, 4(5)-1,2,3,4(5)-tetrazoles. In the case of pyrazole, 3,5-disubstituted derivatives have also been computed, including four dimers.Dedicated to our friend Professor Vladimir I. Minkin on his 70th anniversary.     

One-pot facile synthesis,crystal structure and antifungal activity of 1,2,3-triazoles bridged with amine-amide functionalities

A library of twenty five 1,2,3-triazoles bridged with amine-amide functionalities have been synthesized from reaction of N-substituted(prop-2-yn-1-yl)amines (2a–2e), 2-bromo-N-arylacetamides (4a–4e) and sodium azide through copper(I)-catalyzed alkyne-azide cycloaddition. The synthesized compounds were characterized by using FTIR, ¹H NMR, ¹³C NMR, and HRMS techniques. The structures of synthesized 5a (CCDC 1569245) and 5h (CCDC 1569249) were also confirmed by X-ray crystallography. Antifungal evaluation of newly synthesized triazoles was carried out against – Candida albicans and Aspergillus niger. Biological screening of synthesized 1,2,3-triazoles revealed moderate to good antifungal activity against tested strains.     

ZnO nanoparticles-mediated regioselective synthesis of methyl-N-alkylated 1,2,3-triazole-4-carboxylates

The 1,2,3-triazoles are versatile synthetic intermediates of many biologically active compounds, and their N-1 substituted analogues are potential pharmaceutically important derivatives. In this study, an efficient regioselective N-alkylation reaction of methyl-1H-1,2 3-triazole-4-carboxylate 3 with alkyl halides 4 catalyzed by ZnO nanoparticles in the presence of potassium hydroxide as base and DMSO as solvent is reported which leads to methyl N ₁-alkylated 1,2,3-triazole-4-carboxylates 5 in good yields.     

Dipole moments. Structure and conformation of asymmetrically 4,5-substituted 1-(α-aroyloxyarylideneamino)-1,2,3-triazoles

The dipole moments of several asymmetrically 4,5-substituted 1-(α-aroyloxyarilideneamino)-1,2,3-triazoles, produced by oxidation of bis-aroylhydrazones of α-dicarbonyl compounds, were measured in benzene solution. The structure and the probable conformation of each of these compounds was determined by comparing their experimental and theoretical dipole moments. It has been found that when one of the substituents R₁ or R₂ is an aryl group, it is located at the 4-position of the triazole ring. Considering the conformation of the ester-imino function, it has been found to be the same as that of symmetrically substituted derivatives.     

Synthesis of 1,2,3,4-tetrazine 1,3-dioxides annulated with 1,2,3-triazoles and 1,2,3-triazole 1-oxides

1,2,3,4-Tetrazine 1,3-dioxides annulated with 1,2,3-triazoles and 1,2,3-triazole 1-oxides have been synthesized by the reaction of 4-amino-5-(tert-butyl-NNO-azoxy)-2-R-2H-1,2,3-triazoles (R=Me, i-Pr, t-Bu) and their 1-oxides (R=H, Me, Et, i-Pr) with the HNO₃/H₂SO₄/Ac₂O system. Their thermal stability, spectroscopic, and X-ray properties have been studied.     

Gem-dinitro compounds in organic synthesis. 3. Syntheses of 4-nitro-1,2,3-triazoles from gem-dinitro compounds

Several chemoselective syntheses have been developed for 4-nitro-1,2,3-triazoles from sodium azide and gem-dinitroethylenes prepared from readily available transformation products of dinitroacetic acid ester: N-(,-dinitroethyl)-N,N-dialkylamines, 2,2-dinitroethanol acetate, a mixture of dinitroacetic acid ester with aliphatic aldehydes, or 1,1,1-trinitroalkanes. Hitherto-unknown 4-nitro-5-amino- and 4,5-dinitro-1,2,3-triazoles have been synthesized via successive transformations of the CH₃ groups in 5-nitro-4-methyltriazole. Nitration of 4-nitro-1,2,3-triazole with nitronium fluoroborate or acetyl nitrate gave an unknown 2,4-dinitro-1,2,3-triazole.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Moscow 117913. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 4, pp. 958–966, April, 1992.     

Synthesis and properties of 5-substituted 1-dinitromethyl-3-nitro-1 <Emphasis Type="Italic">H</Emphasis>-1,2,4-triazoles

Denitration of 5-R-substituted 3-nitro-1-trinitromethyl-1H-1,2,4-triazoles (R = CH₃, Cl, Br, N₃, NH₂) by the action of potassium iodide or hydroxylamine, followed by treatment with sulfuric acid, gave the corresponding 1-dinitromethyl derivatives which were shown to be very strong CH acids (pK _a ?0.55 to ?1.62).