Specificity of the reaction of β-carboxyvinyl(triphenyl)phosphonium chloride with azoles

Reactions of pyrazole, 3,5-dimethylpyrazole, 1,2,4-triazole, 5-aminotetrazole, and imidazole with β-carboxyvinyl(triphenyl)phosphonium chloride in boiling acetonitrile are accompanied by elimination of azole with formation of the initial salt and elimination of triphenylphosphine to give the corresponding azole hydrochloride and α-azolyacrylic acid. In all cases, ethylenebis(triphenylphosphonium) dichloride was formed, and the reactions with the most nucleophilic 3,5-dimethylpyrazole and imidazole also led to their adducts with α-azolylacrylic acid. In the reactions of pyrazole and 3,5-dimethylpyrazole with β-carboxyvinyl-(triphenyl)phosphonium chloride at room temperature, the conesponding addition products were isolated in almost quantitative yield.     

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.     

蝎型钒氧苯甲酸配合物的合成、结构及量化计算

设计合成了两种以聚吡唑硼酸盐、苯甲酸为配体的钒氧配合物VO[HB(pz)3](pzH)(C6H5COO)(1)和VO[HB(3,5-Me2pz)3](3,5-Me2pzH)(C6H5COO)(2)((HB(pz)3: 聚吡唑硼酸钠盐; pzH: 吡唑; HB(3,5-Me2pz)3: 聚甲基吡唑硼酸钠盐; 3,5-Me2pzH: 3,5-二甲基吡唑). 通过元素分析、红外光谱和X射线单晶衍射方法对配合物进行了表征. 并结合从头计算结果进一步分析了配合物的稳定性及分子中配键的共价特征. 分析结果表明, 配合物2的稳定性大于配合物1, 中心钒原子周围的价键类型都属于共价键范畴, 键序分析结果与晶体结构测定的键长结果是一致的.     

Nitropyrazoles 22. On reactivity of 3,5-dinitro-4-(phenylsulfonyl)pyrazole and its N-methyl derivative

3,5-Dinitro-4-(phenylsulfonyl)pyrazole (5) obtained by oxidation of 3,5-dinitro-4-(phenylthio)pyrazole with 30% H₂O₂ in AcOH was involved into nucleophilic substitution reaction with thiophenol, which proceeded with substitution of the phenylsulfonyl group at position 4. N-Methyl-3,5-dinitro-4-(phenylsulfonyl)pyrazole obtained by methylation of 5 with dimethyl sulfate was involved into nucleophilic substitution reaction with thiophenol, p-bromophenol, and morpholine with the regioselective substitution of the nitro group at position 5 to form 5-R-3-nitro-4-(phenylsulfonyl)pyrazoles.     

Alkylating nucleosides. 3. The reaction of 3,5-dimethylpyrazole nucleosides with N-bromosuccinimide

Bromination of 3,5-dimethylpyrazole nucleosides with N-bromosuccinimide gave the corresponding 4-bromo-3,5-dimethylpyrazole, 3-methyl-5-(bromomethyl)pyrazole and 4-bromo-3-methyl-5-(bromomethyl)pyrazole nucleosides. Structural assignments were made on basis of analytical and ¹ H nmr spectral data. All of the bromomethylpyrazole nucleosides described showed cytostatic activity against HeLa cell sultures.     

Unusual reaction between (nitrile)Pt complexes and pyrazoles: substitution proceeds via metal-mediated nitrile-pyrazole coupling followed by elimination of the nitrile

The reaction of platinum(IV) complex trans-[PtCl4(EtCN)2] with pyrazoles 3,5-RR'pzH (R/R' = H/H, Me/H, Me/Me) leads to the formation of the trans-[PtCl4{NH=C(Et)(3,5-RR'pz)}2] (1-3) species due to the metal-mediated nitrile-pyrazole coupling. Pyrazolylimino complexes 1-3 (i) completely convert to pyrazole complexes cis-[PtCl4(3,5-RR'pzH)2] by elimination of EtCN upon reflux in a CH2Cl2 solution or upon heating in the solid state; (ii) undergo exchange at the imino C atom with another pyrazole different from that contained in the pyrazolylimino ligand. The reaction of trans-[PtIICl2(EtCN)2] and 3,5-RR'pzH, conducted under conditions similar to those for trans-[PtIVCl4(EtCN)2], is much less selective, and the composition of the products strongly depends on the pyrazole employed: (a) with pzH, the reaction gives a mixture of three products, i.e., [PtCl2NH=C(Et)pz-kappa2N,N}] (4), [PtCl(pzH){NH=C(Et)pz-kappa2N,N}]Cl (5), and [Pt(pzH)2{NH=C(Et)pz-kappa2N,N}]Cl2 (6) (complexes 5 and 6 are rather unstable and gradually transform to trans-[PtCl2(pzH2] and [Pt(pzH)(4)]Cl(2) and free EtCN); (b) with 3,5-Me(2)pzH, the reaction leads to the formation of [PtCl2NH=C(Et)(3,5-Me2pz)-kappa2N,N}] (7) and [PtCl(3,5-Me2pzH)3]Cl (8); (c) in the case of asymmetric pyrazole 3(5)-MepzH, which can be added to EtCN and/or bind metal centers by any of the two nonequivalent nitrogen sites, a broad mixture of currently unidentified products is formed. The reduction of 1-3 with Ph3P=CHCO2Me in CHCl3 allows for the formation of corresponding platinum(II) compounds trans-[PtCl2{NH=C(Et)(3,5-RR'pz)}2] (9-11). Ligands NH=C(Et)(3,5-RR'pz) (12-14) were almost quantitatively liberated from 9-11 with 2 equiv of 1,2-bis-(diphenylphosphino)ethane in CDCl3, giving free imines 12-14 in solution and the precipitate of trans-[Pt(dppe)2](Cl)2. Pyrazolylimines 12-14 undergo splitting in CDCl3 solution at 20-25 degrees C for ca. 20 h to furnish the parent propiononitrile and the pyrazole 3,5-RR'pzH, but they can be synthetically utilized immediately after the liberation.     

Synthesis of New Fused and Spiro Heterocyclic Systems from 3,5‐Pyrazolidinediones

4‐Bromo‐1‐phenyl‐3,5‐pyrazolidinedione 2 reacted with different nucleophilic reagents to give the corresponding 4‐substituted derivatives 3–8 . The cyclized compounds 9–11 were achieved on refluxing compounds 3 , 4 or 6_a in glacial acetic acid or diphenyl ether. 4,4‐Dibromo‐1‐phenyl‐3,5‐pyrazolidinedione 12 reacted with the proper bidentates to give the corresponding spiro 3,5‐pyrazolidinediones 13–15 , respectively. The 4‐aralkylidine derivatives 16_a‐c , were subjected to Mannich reaction to give Mannich bases 17_a‐c‐22_a‐c , respectively. 4‐(p‐Methylphenylaminomethylidine)‐1‐phenyl‐3,5‐pyrazolidinedione 23 or 4‐(p‐methylphenylazo)‐1‐phenyl‐3,5‐pyrazolidinedione 29 were prepared and reacted with active nitriles, cyclic ketones and N,S‐acetals to give pyrano[2,3‐c]pyrazole, pyrazolo[4′,3′:5,6]pyrano[2,3‐c]pyrazole, spiropyrazole‐4,3′‐pyrazole and spiropyrazole‐4,3′‐[1,2,4]triazolane derivatives 24–34 , respectively.     

In situ ATR-FTIR Combined with SIMPLISMA Algorithm to Investigate the Synthesis Mechanism of 4-Amino-3, 5-dimethyl Pyrazole

In situ attenuated total refletion-Fourier transform infrared spectroscopy(ATR-FTIR) was used to monitor and acquire spectral information on the synthesis of 4-amino-3,5-dimethyl pyrazole. Principal component analysis(PCA) was used to determine the number of principle components(PCs). The score vectors of the PCs were analysed using the simple-to-use interactive self-modelling mixture analysis(SIMPLISMA) algorithm to obtain spectral and concentration profiles for the reactants, intermediates and product. The vibrational frequencies of the interme-diates were calculated via density functional theory(DFT) at the level of the B3LYP/6-311++G(d,p) basis set, and the geometrical configurations of the intermediates were simultaneously optimized. Finally, a reasonable synthesis mechanism for 4-amino-3,5-dimethyl pyrazole was determined based on the changes observed in the feature peaks. The results from the SIMPLISMA algorithm correlated well with the quantum chemistry calculations. This proved that the SIMPLISMA algorithm combined with ATR-FTIR can be used to determine the synthesis mechanism for 4-amino-3,5-dimethyl pyrazole and can even provide a new, useful method to explore dynamic synthesis reaction mechanisms.     

Nucleophilic substitution of chlorine atoms in polyvinyl chloride

To modify properties of polyvinyl chloride, its chlorine atoms were substituted using sodium salts of pyrazole, 3,5-dimethylpyrazole, and 2-mercaptobenzimidazole.     

Studies With Pyrazol-3-Carboxylic Acid Hydrazide: The Synthesis of New Pyrazolyloxadiazole and Pyrazolyltriazole Derivatives

A simple and versatile method for the synthesis of pyrazol-3-yl-1,3,4-oxadiazole, pyrazol-3-yl-1,2,4-triazole, (1,5-diphenylpyrazol-3-yl)-(3,5-dimethyl-1-carbonyl)pyrazole, and (1,5-diphenylpyrazol-3-yl)-(5-hydroxy-3-metheyl-1-carbonyl)pyrazole derivatives from 1,5-diphenylpyrazole-3-carboxylic acid hydrazide has been developed.     

Hydrothermal synthesis,crystal structure and characterization of a new 1-D supramolecular ladder based on a binuclear CdII complex [Cd2L4(3,5-DNBA)2](H2O) with L as a bridging ligand (L=3-(2-pyridyl)pyrazole; 3,5-DNBA=3,5-dinitrobenzoate)

A new 1-D cadmium(II) mixed ligand dimer supramolecular ladder [Cd₂ L ₄(3,5-DNBA)₂]H₂O (1), (L?=?3-(2-pyridyl)pyrazole and 3,5-DNBA?=?3,5-dinitrobenzoate) was synthesized by hydrothermal methods. X-ray structural analysis of complex 1 revealed that two cadmium(II) cores are bridged by two deprotonated pyrazole groups of L, leading to dinuclear cadmium(II) [Cd₂ L ₄(3,5-DNBA)₂]. The dimers are joined by hydrogen-bonding interactions between two different cadmium(II) dimers to form a one-dimensional ladder-like framework and stabilized by weak π–π interactions. Moreover, the fluorescence spectrum of compound 1 exhibits blue fluorescent emission in the solid state at room temperature.     

Electrosynthesis of 4-bromosubstituted pyrazole and its derivatives

Electrosynthesis of 4-bromosubstituted pyrazole and its derivatives was carried out by bromination of initial pyrazoles on Pt anode in NaBr aqueous solutions under the conditions of diaphragm galvanostatic electrolysis. A donor substituent (Me or Et) in pyrazole ring was shown to promote to the bromination process, while an acceptor substituent (NO₂ or COOH) does not produce a significant effect to this process. Thus, the yield of 4-bromosubstituted derivatives from bromination of 3,5-dimethylpyrazole, 1,5-dimethylpyrazole, 3-nitropyrazole, pyrazole-3(5)-carboxylic acid, 1-methylpyrazole-3-carboxylic acid, 1-methylpyrazole-5-carboxylic acid, 1-ethylpyrazole-5-carboxylic acid, and 1-methylpyrazole-3,5-dicarboxylic acid amounted 70, 94, 88, 89, 84, 78, 89, and 84%, respectively.     

Spectroscopic study on charge transfer molecular complexes of pyrazole derivatives with some pi-electron acceptors

Charge transfer molecular complexes of some pyrazole donors (pyrazole, 4-methylpyrazole, 3-methylpyrazole and 3,5-dimethylpyrazole) with 2,3-dichloro-5,6-dicyano-1,4-p-benzoquinone and tetracyanoethylene as pi-electron acceptors have been studied in CH2Cl2 at 25 degrees C. Spectral characteristics and stability constants of the formed charge transfer (CT) complexes are discussed in terms of the nature of donor and acceptor molecular structure, as well as in relation to solvent polarity. Thermodynamic parameters (deltaH, deltaG and deltaS) associated with CT complex formation are also examined. It was concluded that the formed CT complexes are of n-pi type with 1:1 (D:A) composition.     

Sequential functionalization of pyrazole 1-oxides via regioselective metalation: synthesis of 3,4,5-trisubstituted 1-hydroxypyrazoles

A range of 3,5-diarylated and 3,4,5-triarylated 2-(4-methoxybenzyl)pyrazole 1-oxides have been prepared by regioselective deprotonation at C-5 or bromine-magnesium exchange at C-3 or C-4 followed by transmetalation with ZnCl(2) and palladium(0)-catalyzed cross-coupling. Furthermore, the metalated pyrazole 1-oxides could be trapped with electrophiles. The sequential metalation/functionalization of the pyrazole 1-oxides may follow the order C-5, C-3, C-4, or alternatively the order C-3, C-5, C-4. The 4-methoxybenzyl group of the functionalized 2-(4-methoxybenzyl)pyrazole 1-oxides could be removed by treatment with TFA and i-Pr(3)SiH in CH(2)Cl(2), providing the corresponding functionalized 1-hydroxypyrazoles.     

Electrosynthesis of 4-chloro derivatives of pyrazole and alkylpyrazoles

Electrosynthesis of 4-chloro-substituted derivatives of pyrazole and its alkyl derivatives is carried out via the chlorination of original pyrazoles on a Pt anode in aqueous NaCl solutions under conditions of galvanostatic diaphragm electrolysis. The efficiency of this process is shown to depend on the structure of starting pyrazoles, particularly, the donor-acceptor properties of substituents, the position of the latter in the pyrazole ring, and the concomitant contribution of side reactions. Thus the yield of 4-chlorosubstituted products at the chlorination of pyrazole, 3,5-dimethylpyrazole, 1,5-dimethylpyrazole, and 3-nitropyrazole is 68, 92, 53, and 79%, respectively. By the example of 1,5-dimethylpyrazole, the possibility of electrochemical chlorination to the side chain of pyrazoles was demonstrated.     

Pyrazole complexes as anion receptors

The behavior of the receptors [Re(CO)3(Hdmpz)3]BAr'4 (Hdmpz = 3,5-dimethylpyrazole) (1) and [Re(CO)3(HtBupz)3]BAr'4 (HtBupz = 3(5)-tert-butylpyrazole) (2; Ar' = 3,5-bis(trifluoromethyl)phenyl) toward the anions fluoride, chloride, bromide, iodide, hydrogensulfate, dihydrogenphosphate, nitrate, and perrhenate was studied in CD3CN solution. In most cases, the receptors were stable. Anion exchange was fast, and binding constants were calculated from the NMR titration profiles. The structure of the adduct [Re(CO)3(HtBupz)3] x NO3 (3) was determined by X-ray diffraction. Two pyrazole moieties are hydrogen-bonded to one nitrate oxygen atom, and the third pyrazole moiety is hydrogen-bonded to an oxygen atom of an adjacent nitrate, leading to infinite chains. The structure of the adduct [Re(CO)3(Hdmpz)3]BAr'4acetone (4), also determined by X-ray diffraction, showed a similar interaction of two pyrazole N-H groups with the acetone oxygen atom. F- and H2PO4(-) deprotonate the receptors, and HSO4(-) decomposed 1. The structure of one of the decomposition products (5), determined by X-ray diffraction, is consistent with pyrazole protonation and substitution by sulfate.     

Mesomorphism of a tetrahedral zinc complex

Thermotropic smectic phases have been observed for the first time in a zinc coordination complex with tetrahedral geometry; this complex, which contains the pyrazole dimer bis[3,5-bis(p-decyloxyphenyl)pyrazolyl]ethane as the ligand, exhibits fluorescence.     

Electrosynthesis of 4-iodopyrazole and its derivatives

Electrosynthesis of 4-iodo-substituted pyrazoles has been accomplished by iodination of the corresponding precursors on a Pt-anode in aqueous solutions of KI under conditions of the diaphragm galvanostatic electrolysis. Efficiency of the process depends on the donor-acceptor properties of substituents and their positions in the pyrazole ring. Thus, iodination of pyrazole, 3,5-dimethylpyrazole, 3-nitropyrazole, 1-methylpyrazole, 1,3-dimethylpyrazole, pyrazole-3(5)-carboxylic acid or methyl esters furnished 4-iodo derivatives in 57, 86, 2, 5, 35, 30, and 40% yields, respectively.     

Synthesis of 1,8-di(pyrazol-1-yl)-3,6-dioxaoctane and its derivatives

From pyrazole, 3,5-dimethylpyrazole, and 1,8-dibromo-3,6-dioxaoctane in a superbasic medium KOH-DMSO the corresponding 1,8-di(pyrazol-1-yl)-3,6-dioxaoctanes were synthesized and converted into iodo-, nitro-, amino-, and formylderivatives.     

Influence of steric strain of S,N-heterocycles derivative ligands on the coordination geometry in cadmium(II) nitrato complexes

The new ligands 2-(3,5-dimethyl-1-pyrazolyl)-2-thiazoline (DMPyTn) and 2-(3,5-diphenyl-1-pyrazolyl)-2-thiazoline (DPhPyTn) have been synthesized and characterized, and six cadmium(II) nitrato complexes with these two ligands and four other pyrazole/S,N-heterocyclic derivative ligands with different steric features, previously reported, have been prepared and structurally characterized by means of elemental analysis, single crystal X-ray diffraction and IR spectra, with the objective of determining the role played by the steric strains of the ligands on the metal ion coordination index and geometry. The effect of two factors has been analyzed: the bulk of the pyrazole ring substituents and the size of the S,N-heterocycle. The data indicate that there is a clear influence of the size of the organic ligands on the coordination environment of the Cd(II) ion.