Synthesis and characterization of a chalcone-derived epoxy containing pyrazoline ring with excellent flame resistance

Traditional epoxy resins are made by the reaction of petroleum-based bisphenol A and epichlorohydrin. The disadvantages of these petroleum-based epoxy including certain biological toxicity and flammability. To solve these problems, we first synthesized a diphenol compound 3,5-(4-hydroxyphenyl)-2-pyrazoline (TPP), which was prepared by condensation reaction of bio-based chalcone with hydrazine hydrate to replace standard petroleum-based bisphenol A. Then it was condensed with epichlorohydrin under alkaline condition to form a fully aromatic pyrazoline ring epoxy (TPP-EP). For further research, we use 4,4′-diaminodiphenylmethane (DDM) as the curing agent. When compared with bisphenol A epoxy resin (DGEBA/DDM), TPP-EP/DDM possessed a higher glass transition temperature (233°C vs. 176°C), and even showed that the residual carbon (in N2) and the storage modulus (at 30°C) increased by 201% and 74%, respectively. What’s more, TPP-EP/DDM system also had good inherent flame retardancy. The limiting oxygen index of TPP-EP/DDM was 33.1, reaching the V-0 level tested by UL-94. From the cone test, the THR, p-HRR, p-SPR and TSP values of TPP-EP/DDM systems also showed different degrees of reduction. Since TPP-EP contained tertiary amine active groups that could be used as a kind of catalytic curing agents for epoxy resins, thus the compound had certain self-curing properties. This work was of great significance for the synthesis of pyrazoline bio-based environmentally friendly flame-retardant epoxy resin.

Synthesis, crystal structure and Hirshfeld surface analysis of 4-[3-(4-hydroxyphenyl)-4,5-dihydro-1H-pyrazol-5-yl]-2-methoxyphenol monohydrate

In the title pyrazoline derivative, C16H16N2O3·H2O, the pyrazoline ring has an envelope conformation with the substituted sp 2 C atom on the flap. The pyrazoline ring makes angles of 86.73 (12) and 13.44 (12)° with the trisubstituted and disubstituted benzene rings, respectively. In the crystal structure, the molecules are connected into chains running in the b-axis direction by O—H...N hydrogen bonding. Parallel chains interact through N—H...O hydrogen bonds and π–π stacking of the trisubstituted phenyl rings. The major contribution to the surface contacts are H...H contacts (44.3%) as concluded from a Hirshfeld surface analysis.

A REVIEW ON ANTI-INFLAMMATORY POTENTIAL OF SUBSTITUTED PYRAZOLINE DERIVATIVES SYNTHESISED FROM CHALCONES

The pyrazoline ring is a ubiquitous structural feature of many natural and synthetic compounds with potent anti-inflammatory activity. The creation of novel pyrazoline derivatives and examination of their chemical and biological behaviour have gained additional focus in the current decade. Pyrazolines and its fused heterocyclic derivatives tested with anti-inflammatory activity constitute a significant class of compounds for novel drug evolution. Pyrazoline nucleus when linked with different substituents like alkyl, aromatic, heterocyclic rings and many other groups at different positions on the ring shows considerable to more effective anti-inflammatory activity. This article presents a comprehensive review of the anti-inflammatory activity of some novel derivatives of pyrazoline ring.

1-ALKYL-3-METHYL-4-HYDROXYIMINO-2-PYRAZOLINE-5-ONES AS EXTRACTION REAGENTS

With nitrosation of the corresponding 1-R-3-methylpyrazole-5-one (R = C4H9, C5H11, C6H13, C7H15, C8H17, C6H5) in acidic aqueous methanolic medium at 0-5 °C a series of 1-alkyl-3-methyl-4-hydroxyimino-2-pyrazolin-5-ones with a yield of 72-85% were synthesized. The compounds are soluble in CHCl3, C2H4Cl2, C6H5CH3, i-C4H9OH, CCl4, C2H5OH, slightly soluble in C6H14, H2O. They can be recrystallized from a mixture of C6H14: C6H5CH3 = 5: 1 or isooctane. The structure of the compounds was confirmed by the data of ECR, IR, Raman spectroscopy and TLC data. The interphase distribution of oxyiminopyrazolones between chloroform and aqueous solutions was studied as a function of pH. In alkaline media, the reagents completely transferred into the aqueous phase. In acidic solutions, up to 1 mol/l HCl, the compounds are in the organic phase. The maximum values of the partition coefficient are observed for the reagents with the maximum length of the aliphatic radical. The effect of the length of aliphatic radical at the first position of the pyrazoline ring on their extraction properties were studied by example of extraction of nickel and copper (II) ions. The length of the radical does not affect the composition of the recoverable complexes of nickel and copper (II). In all cases the ratio is close to 1:2. Extraction proceeds through a cation-exchange mechanism. Replacement of the phenyl radical in the first position of the pyrazoline ring by an aliphatic resulted to the increase in partition constants of the reagents between chloroform and aqueous solutions. The range of pH values of the maximum extraction of elements was widened. The capacity of the extractant for metals also increased. At the same time, the pH50 extraction values remained practically unchanged. In the case of 0.05 mol/l solution of 1-phenyl-3-methyl-4-oxyimino-2-pyrazolin-5-one in chloroform, when the extract was saturated with the metal ion, precipitation of the complex was observed.For citation:Lesnov A.E., Pavlov P.T., Pustovik L.V., Sarana I.A. 1-Alkyl-3-methyl-4-hydroxyimino-2-pyrazoline-5-ones as extraction reagents. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 5. P. 30-36.

3-(2-Hydroxy-4-methoxyphenyl)-N-(2-methoxyphenyl)-5-(naphthalen-1-yl)-4,5-dihydro-1H-pyrazole-1-carbothioamide

In the title molecule, C28H25N3O3S, the dihedral angles formed by the naphthalene ring system and the benzene rings are 73.03 (13) and 74.04 (11)°. The benzene rings attached to the central pyrazoline ring are almost coplanar, as indicated by the dihedral angle of 2.22 (10)° between them. The C atom of the methoxy group of the phenol ring is essentially coplanar with the ring [C—C—O—C = −0.3 (3)°], whereas the C atom of the methoxy group of the thioamide benzene ring is slightly twisted [C—C—O—C = 5.4 (3)°]. An intramolecular O—H...N hydrogen bond generates anS(6) ring motif. In the crystal, pairs of very weak C—H...S interactions form inversion dimers with anR22(18) motif.

Dehydrogenation induced inhibition of intramolecular charge transfer in substituted pyrazoline analogues

Experimental and computational studies reveal that dehydrogenation of the pyrazoline ring modifies its ground and excited state photophysics radically by restricting the ICT process.

Synthesis and characterization of novel benzimidazole embedded 1,3,5-trisubstituted pyrazolines as antimicrobial agents

Efficient syntheses of some new substituted pyrazoline derivatives linked to substituted benzimidazole scaffold were performed by multistep reaction sequences. All the synthesized compounds were characterized using elemental analysis and spectral studies (IR, 1D/2D NMR techniques and mass spectrometry). The synthesized compounds were screened for their antimicrobial activity against selected Gram-positive and Gram-negative bacteria, and fungi strain. The compounds with halo substituted phenyl group at C5 of the 1-phenyl pyrazoline ring (15, 16 and 17) showed significant antibacterial activity. Among the screened compounds, 17 showed most potent inhibitory activity (MIC = 64 ?g mL-1) against a bacterial strain. The tested compounds were found to be almost inactive against the fungal strain C. albicans, apart from pyrazoline-1-carbothiomide 21, which was moderately active.

(5-Hydroxy-3-methyl-5-trifluoromethyl-4,5-dihydro-1H-pyrazol-1-yl)(2-hydroxyphenyl)methanone

In the title compound, C12H11F3N2O3, the hydroxyphenyl ring is twisted by 35.42 (11)° from the plane of the pyrazoline ring. The keto O atom is involved in two intramolecular O—H...O hydrogen bonds, which generateS(6) loops. As result, a weak intramolecular C—H...N contact is formed, which generates anS(7) ring motif. In the crystal, pairs of O—H...O hydrogen bonds link molecules into inversion dimers with anR22(16) motif. The dimers are linked by parallel-slipped π–π interactions [intercentroid distance = 3.8438 (19) Å], forming columns along thec-axis direction.

Crystal structure of 1-{3-(4-methylphenyl)-5-[(E)-2-phenylethenyl]-4,5-dihydro-1H-pyrazol-1-yl}ethan-1-one

The title compound, C20H20N2O, was studied as a part of our work on pyrazoline derivatives. It represents atrans-isomer. The central pyrazoline ring adopts an envelope conformation with the asymmetric C atom having the largest deviation of 0.107 (1) Å from the mean plane. It forms dihedral angles of 6.2 (1) and 86.4 (1)° with the adjacentp-tolyl and styrene groups, respectively. In the crystal, C—H...O interactions link molecules into infinite chains along thecaxis.

Crystal structure of 3-methoxy-2-[5-(naphthalen-1-yl)-4,5-dihydro-1H-pyrazol-3-yl]phenol

In the title compound, C20H18N2O2, the central pyrazoline ring has an envelope conformation with the atom substituted by the naphthalene ring as the flap. It bridges a benzene ring and a naphthalene ring system which are almost normal to one another, making a dihedral angle of 82.03 (6) °. There is an intramolecular O—H...N hydrogen bond forming anS(6) ring motif. In the crystal, molecules are linked by pairs of N—H...π interactions, forming inversion dimers. There are also C—H...π interactions present and the dimers are linkedviaC—H...O hydrogen bonds, forming ribbons propagating along thea-axis direction.