Nitropyrazoles 23. Synthesis of substituted N-amino-3-nitro-5-R-pyrazoles

The study is devoted to nucleophilic substitution of nitro groups in 1-amino-3,5-dinitropyrazole (1) and its amino group derived analogs. Compound 1 upon treatment with S-nucleophiles undergoes regioselective substitution of the nitro group at position 5. Azomethine 5 obtained by the condensation of 1 with benzaldehyde gives the nucleophilic substitution reaction with S-, O-and N-nucleophiles also with involvement of the nitro group at position 5. The synthesized 5-R-substituted azomethines 7–9 upon treatment with hydrazine hydrate form N-amino-5-R-3-nitropyrazoles and benzaldazine.     

Synthesis of 4-methoxy-3,5-dinitrobenzaldehyde: a correction to supposed tele nucleophilic aromatic substitution

1,3-Dinitro-5-trichloromethylbenzene (2) was reacted with sodium methoxide in an attempt to prepare 4-methoxy-3,5-dinitrobenzaldehyde (7) via a reported tele nucleophilic aromatic substitution. The product from this reaction was methyl 3,5-dinitrobenzoate (5) and not the methoxy aldehyde as had been reported. The desired product was prepared by conventional nitration methodology from 4-methoxy-3-nitrobenzaldehyde.     

Some new energetic benzaldoximes

5-Nitro-2-hydroxy benzaldoxime (I), 3-nitro-4-hydroxy benzaldoxime (II), 3,5-dinitro-2-hydroxy benzaldoxime (III), and 3,5-dinitro-4-hydroxy benzaldoxime (IV) were prepared from their respective nitrated aldehydes. Prepared oximes were characterized by IR spectroscopy, elemental analysis, and mass spectrometry. Suitable crystals of compounds II and III were obtained and molecular structures were determined by means of the single crystal XRD method. All benzaldoximes were investigated by TG. At temperatures above 140 °C, it was observed that compounds II and IV lost one H₂O and was converted to the respective benzonitriles. Only thermal analysis peaks of 3,5-dinitro-4-hydroxy benzonitrile (V) were found proper for both experimental and theoretic calculations; whereas, compounds I and III were converted to phenoxazines by Beckmann rearrangement along with dehydration. Beckmann product of compound III is referred as compound VI and its tautomer as compound VII. Similarly only 3,5-dinitro phenoxazine (VIII) was investigated experimentally and theoretically since its thermal analysis peaks were proper for the purpose. DFT-based structure optimizations and frequency analyses were performed at the B3LYP/cc-pVDZ level of theory. The enthalpies of formation for compounds III–VIII were calculated by means of the complete basis set (CBS-4M) method of Petersson and coworkers to obtain accurate energies. The enthalpies of decomposition for compounds III and IV were obtained from calculated enthalpies of formation according to Hess’ law and were compared with the experimental values which were available from DSC analyses and were found to be in good agreement with the theoretic values.     

Synthese von (5,10)-(7,8)-Bisepoxiden aus α- und β-4-Phenyl-1,2,4-triazolin-3,5-dion-Addukten von Vitamin D3 und Röntgenstrukturanalyse eines der Benzoylderivate

Oxidation of the α- and β-4-phenyl-1,2,4-triazolin-3,5-dione adducts of vitamin D₃ (2 and1) withMCPBA yields two diastereomeric mixtures of the (5,10)-(7,8)-dioxiranes3 a,3 b,3 c and4 a,4 b respectively. The corresponding benzoates5 a,5 b,6 a and6 b were prepared and the X-ray crystal structure of5 b was determined. This analysis proved5 b to be the (5R, 1 OS)-(7R, 8R)-dioxirane of the β-resp. (6S)-4-phenyl-1,2,4-triazolin-3,5-dione adduct1 of vitamin D₃.     

Synthesis and evaluation of substituted pyrazoles palladium(II) complexes as ethylene polymerization catalysts

The substituted pyrazole palladium complexes, (3,5-^tBu₂pz)₂PdCl₂ (1) (3,5-Me₂pz)₂PdCl₂ (2), (3-Mepz)₂PdCl₂ (3) and (pz)₂PdCl₂ (4) (pzH=pyrazole), can be prepared from the reaction of (COD)PdCl₂ with the appropriate pyrazole. The chloromethyl derivative, (3,5-^tBu₂pz)₂PdCl(Me) (5), was prepared from (COD)PdClMe and ^tBu₂pzH. X-ray crystal structure determination of 1 and 5 established their structures in the solid state to be the trans-isomer. After activation of 1-4 and 5 with methylaluminoxane (MAO) the resulting palladium complexes were used as catalysts in ethylene polymerization, yielding linear high-density polyethylene (HDPE). The highest activity was observed for (3,5-^tBu₂pz)PdClMe.     

The Synthesis and Characterization of Re2(Xap)4Cl2 Compounds

Five dirhenium(III) compounds, Re₂(3,5-(CH₃)₂ap)₄Cl₂ (1), Re₂(ap)₄Cl₂ (2), Re₂(3-MeOap)₄Cl₂ (3), Re₂(3-Clap)₄Cl₂ (4), and Re₂(3,5-Cl₂ap)₄Cl₂ (5), were synthesized and characterized, where 3,5-(CH₃)₂ap, ap, 3-MeOap, 3-Clap and 3,5-Cl₂ap are 2-(3,5-dimethylanilino)pyridinate, 2-anilinopyridinate, 2-(3-methoxyanilino)pyridinate, 2-(3-chloroanilino)pyridinate and 2-(3,5-dichloroanilino)pyridinate, respectively. Structural studies revealed the Re–Re bond lengths ranging from 2.2214(4) to 2.2262(11) Å, signifying that the dirhenium core maintains its quadruple bond. The asymmetric nature of 2-anilinopyridinate ligands resulted in several possible regioisomers: compounds 1 and 4 adopt a cis-(2,2) arrangement, while compounds 2 and 5 assume trans-(2,2) and (3,1) arrangements, respectively. All five compounds display three (quasi)reversible one electron couples, two oxidations and one reduction, and their electrode potentials correlate linearly with the Hammett constant of the aniline substituent.     

Nitropyrazoles 16. The use of methoxymethyl group as a protecting group for the synthesis of 4-methyl-3-nitro-5-R-pyrazoles

4-Methyl-3,5-dinitropyrazole prepared by nitration of 1,4-dimethylpyrazole readily reacts with methoxymethyl chloride and methyl vinyl ketone in acetonitrile in the presence of a base giving 1-methoxymethyl-4-methyl-3,5-dinitropyrazole and 4-methyl-3,5-dinitro-1-(3-oxobutyl)pyrazole, respectively. The action of the thioglycolanilide anion on 4-methyl-3,5-dinitro-1-(3-oxobutyl)pyrazole results only in the removal of 1-protecting group and the formation of 2-[(3-oxobutyl)thio]acetanilide, while the action of anionic S-nucleophiles on 1-methoxymethyl-4-methyl-3,5-dinitropyrazole leads to the substitution products of the 5-NO₂ group in which the methoxymethyl group can be removed by acid hydrolysis.     

An efficient 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate (TBTU)-mediated synthesis of 5-(trifluoromethyl)-N-alkyl-1-(3-phenylisoquinoline-1-yl)-1H-pyrazole-4-carboxamides

A series of 5-(trifluoromethyl)-N-alkyl-1-(3-phenylisoquinoline-1-yl)-1H-pyrazole-4-carboxamides 4 has been effectively achieved in high yield and purity from the reaction of pyrazole carboxylic acid 2 with amines 3 in the presence of TBTU as a catalyst and diisopropyl ethylamine as a base in acetonitrile at room temperature.     

Efficient one-pot preparation of bis(pyrazino[2′,3′:4,5]thieno[3,2-d]pyrimidin-4-yl)benzenes based on an aza-Wittig/mediated annulation strategy

Aza-Wittig mediated annulation provides a highly facile and straightforward one-pot strategy for the synthesis of bis(pyrazino[2′,3′:4,5]thieno[3,2-d]pyrimidin-4-yl)benzenes 5 and 7. A tandem aza-Wittig reaction of iminophosphorane 2 with 1,4- or 1,3-phenylene diisocyanate, followed by intramolecular heteroconjugate addition annulation after addition of a nucleophilic reagent (amine, phenol, thiophenol or ROH), in presence of catalytic K₂CO₃ or NaOR, gives selectively the functionalized bis(pyrazinothienopyrimidinones) 5 and 7.     

Nucleophilic amination of 2-iodo-3-nitro-1-(phenylsulfonyl)indole

The reaction of 2-iodo-3-nitro-1-(phenylsulfonyl)indole (2) with amines affords the corresponding 2-amino-3-nitroindoles in excellent yields via nucleophilic aromatic substitution.     

Physico-chemical and thermal characterisation of new Co(II) complexes with pyrazole derivatives

Four new complexes having general formula [CoL₂(acr)₂] (L: 1H-pyrazole (Hpz) (1); 3-methyl-1H-pyrazole (3-Me-Hpz) (2); 4-methyl-1H-pyrazole (4-Me-Hpz) (3); 3,5-dimethyl-1H-pyrazole (Hdmpz) (4); acr: acrylato ion) were synthesised and characterised. The infrared and UV–vis spectral data indicate that these pyrazole derivatives act as unidentate while acrylato ions act as bidentate chelate ligands generating Co(II) complexes with octahedral stereochemistry. TG experiments revealed the nature of complex species as anhydrous and confirmed those compositions. The biological assays revealed a good activity against Bacillus subtilis for all complexes.     

Regioselective synthesis of novel substituted pyrazolo[1,5-a]pyrimidines under solvent-free conditions

A series of 6-(2-hydroxybenzoyl)-5-methyl-7-phenylpyrazolo[1,5-a]pyrimidines 5 have been synthesized directly by the solvent-free reaction between 5-amino-1H-pyrazoles 1 and 3-benzoyl-2-methyl-4H-chromen-4-one 4. This solvent-free reaction proceeds in a regiospecific fashion by intramolecular opening of the γ-pyrone ring in a Michael-type reaction, that followed by cyclization via nucleophilic attack of endocyclic pyrazole nitrogen toward benzoyl group gives the pyrazolo[1,5-a]pyrimidines 5. The use of this method affords high yields in short reaction times.     

Synthesis and Structures of Silver(I) Adducts with 4-Amino-3,5-diisobutyl-4H-1,2,4-triazole: The Identification of a New Type of Ag3tz6 Cluster

Reactions of silver(I) salts with 4-amino-3,5-diisobutyl-4H-1,2,4-triazole (4-NH₂-3,5- ⁱ Bu₂-tz) or 4-amino-3,5-dibutyl-4H-1,2,4-triazole (4-NH₂-3,5-Bu₂-tz) yielded five new adducts, namely, [Ag₂(4-NH₂-3,5- ⁱ Bu₂-tz)₂(NO₃)₂] (1), [Ag₃(4-NH₂-3,5- ⁱ Bu₂-tz)₆](SO₃CF₃)₃ (2), [Ag₃(4-NH₂-3,5- ⁱ Bu₂-tz)₆](ClO₄)₃ (3), [Ag₄(4-NH₂-3,5-Bu₂-tz)₆](ClO₄)₄ (4) and [Ag₄(4-NH₂-3,5-Bu₂-tz)₆](CF₃SO₃)₄ (5). X-ray analyses have been done on the first four adducts, showing that 1 and 4 adopt previously observed Ag₂tz₂ and Ag₄tz₆-a cluster structures, respectively; 2 and 3, on the other hand, contain an unprecedented Ag₃tz₆ cluster, which is closely related to Ag₄tz₆–a cluster by removal of one Ag atom from the latter. The formation of Ag₃tz₆ cluster other than the expected Ag₄tz₆ cluster in 2 and 3 has been tentatively attributed to the steric effect of isobutyl groups.     

Über die Synthese von 1,3-Dihydro-3-(2-dimethylaminoäthyl)-1-(3-thienyl)-benzimidazol-2-onen

The synthesis of 1-(3-thienyl)-benzimidazol-2-ones (3 a and4), described in an earlier paper¹, has been further investigated. The Na-salt of3 a is converted to a benzimidazolone substituted in position 3 (3 b). Dehydrogenation of the thiophene nucleus of3 a with chloranil yields5 a, which undergoes substitution in position 3 with Cl(CH₂)₂N(CH₃)₂ to give5 b. Monochlorination of5 a yields5 c, the structure of which is confirmed by¹H-NMR-spectroscopy.5 d is obtained by reaction of the Na-salt of5 c with Cl(CH₂)₂N(CH₃)₂.      

Synthesis, structure, luminescence properties, quantum chemistry and cytotoxic effects of two vanadium(IV) complexes with polypyrazolylborates, HB(pz)3VO(acac) and HB(3,5-Me2pz)3VO(acac)·CH3CN (pz = pyrazole)

The reaction of VO(acac)₂ (acac = acetylacetonate) with NaHB(pz)₃ (pz = pyrazole) or NaHB(3,5-Me₂pz)₃ in methanol gave vanadium(IV) complexes HB(pz)₃VO(acac) (1) or HB(3,5-Me₂pz)₃VO(acac)·CH₃CN (2), respectively. The complexes 1 and 2 were characterized by elemental analysis, IR, UV-vis, NMR and X-ray diffraction crystallography methods. Complex 1 crystallizes in space group P2₁/c, a = 7.641(2) Å, b = 17.008(4) Å, c = 13.362(2) Å; β = 92.092(17)°, V = 1735.5(7) ų, Z = 4. Complex 2 crystallizes in space group P2₁/c, a = 17.410(13) Å, b = 8.076(16) Å, c = 19.300(13) Å; β = 101.75(5)°, V = 2657(6) ų, Z = 4. X-ray structure analyses have shown that the complexes 1 and 2 are monomeric with a similar coordination environment of the vanadium atom. Luminescence properties and cytotoxic effects of the complexes are discussed. On CBRH-7919 cells, the complexes 1 and 2 caused a slight stimulation of growth at low doses (1–10 μM) and a significant cytotoxic effect at higher doses (100–1000 μM). The electronic structure and the bonding characters of the two complexes were analyzed with ab initio calculations. Original Russian Text Copyright ? 2006 by Y. H. Xing, Z. Sun, W. Zou, J. Song, K. Aoki, and M. F. Ge __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 47, No. 5, pp. 924–932, September–October, 2006.     

Synthesis and oxoanions (dichromate/arsenate) sorption study of N-methylglucamine derivative of calix[4]arene immobilized onto poly[(phenyl glycidyl ether)-co-formaldehyde]

The article describes synthesis as well as the evaluation of sorption properties of new N-methylglucamine substituted calix[4]arene and its poly[(phenyl glycidyl ether)-co-formaldehyde] immobilized product. Firstly, 5,17-bis-[(N-methylglucamine)methyl]-25,26,27,28-tetrahydroxy-calix[4]arene (3) was synthesized by the treatment of calix[4]arene with a secondary amine N-methylglucamine and formaldehyde via Mannich reaction. The immobilization of 3 onto poly[(phenyl glycidyl ether)-co-formaldehyde] to form calixarene based polymer (4) was carried out under suitable reaction conditions via nucleophilic substitution reaction. All the new compounds were characterized by a combination of FT-IR, ¹H-NMR spectroscopic and elemental analysis techniques. The sorption studies of 4 reveal that it is an excellent material for the removal of toxic oxoanions especially arsenate from aqueous environment. To understand the selectivity of 4, we also examined the retention of dichromate anions in the presence of Cl^?, NO₃ ^? and SO₄ ^2? anions at pH 1.5.     

Catechol oxidation: activity studies using electron-rich nitrogen-based ligands

We have studied the oxidation of catechol to o-quinone with atmospheric dioxygen at ambient conditions by in situ generated copper (II) complexes of five electron-rich nitrogen ligands: (3,5-dimethyl-pyrazol-1-yl)-methanol L1; 3-benzylamino-propionitrile L2; 3-[benzyl-(3,5-dimethyl-pyrazol-1-ylmethyl)-amino]-propionitrile L3; {3-[(2-cyano-ethyl)-(1,5-dimethyl-1H-pyrazol-3-ylmethyl)-amino]-propyl}-(1,5-dimethyl-1H-pyrazol-3-ylmethyl)-amino]-propionitrile L4 and 3-[{2-[(2-cyano-ethyl)-(1,5-dimethyl-1H-pyrazol-3-ylmethyl)-amino]-ethyl}-(1,5-dimethyl-1H-pyrazol-3-ylmethyl)-amino]-propionitrile L5. We found that all complexes catalyze the oxidation reaction with different rates depending on three parameters: the nature of the ligand, the nature of ion salts, and the concentration of the complex. The combination of L3(CuSO₄) gave the highest rate of this activity about 8.71 μmol¹/L¹/min¹.     

One-pot microwave-assisted solvent-free synthesis,theoretical and experimental studies on barrier rotation of C–N bond of N-alkenyl-1,2,3-triazoles

The reactions on benzotriazoles continue to happen to reach interesting varieties of their derivatives. This study reports a fast one-pot microwave-assisted solvent-free synthesis of N-alkenyl-1,2,3-benzotriazole (3, 5, and 7) and 1-(2-Alkyloxycarbonyl-vinyl)-1H-[1–3] triazole-4-carboxylic acid methyl ester (8 and 9) derivatives by nucleophilic addition reactions of 1,2,3-benzotriazole (C₆H₅N₃) (1) and 1H-[1–3] triazole-4-carboxylic acid methyl ester (C₄H₄N₃O₂) (1′) with R-propiolates (R = Me, Et; 2 & 4) and phenylacetylene 6 in good yields. The values of activation energy for rotation around C–N bond in the synthesized N-alkenyl-1,2,3-triazole compounds were studied by DFT-B3LYP/6-31G* method.     

Synthesis of (zinc(II) phthalocyanine)-containing cellulose derivative using phthalocyanine-ring formation reaction

2,3-Di-O-myristyl-6-O-(zinc(II) phthalocyaninyl) cellulose (5) was synthesized from cellulose (1) by five reaction steps via 6-O-(3′,4′-dicyanophenyl)-2,3-di-O-myristyl cellulose (4). The key reaction was phthalocyanine-ring formation on a cellulose backbone, that is, the reaction of compound 4 with o-phthalodinitrile in the presence of hexamethyldisilazane and zinc acetate in DMF afforded to compound 5 in 35.4 % yield. Consequently, the degree of substitution with phthalocyanine moieties of compound 5 was 0.38. The LB monolayer film of compound 5 on an indium tin oxide (ITO) electrode was found to show photocurrent generation performance at 680 nm.     

Anion-directed organized assemblies of protonated pyrazole-based ionic salts

The reactions of 3(5)-(4-methoxyphenyl)-5(3)-phenyl-1H-pyrazole (L ¹ ) with nitric acid and 5-(4-benzyloxyphenyl)-3-(furan-2-yl)-1H-pyrazole(L ² ) with hydrochloric acid produced [HL ¹ · NO₃] (Salt-1) and [HL ² · Cl] (Salt-2). The structures of Salt-1 and Salt-2 were determined by single crystal X-diffraction. In Salt-1, HL ¹ showed [2 + 2] binding of NO₃ ^? ions in the solid state to form dimer architecture with R ₁ ² (4) and R ₄ ⁴ (14) graph sets. An anion directed one-dimensional anion-assisted helical chain with active participation of the chloride ion and protonated pyrazole via N–H···Cl hydrogen bonding in Salt-2. In addition, the protonated HL ² molecules interacted with each other through weak C–H···π interactions resulting in the formation of another one-dimensional helical chain.