The structure and thermal properties of novel DOPO-containing 1,3-benzoxazines

Three DOPO (9,10-dihydro-9-oxa-10-phospha-phenanthrene-10-oxide)-containing benzoxazin (3a–3c) were successfully prepared from 2-hydroxybenzaldehyde, p-substituted aniline, and DOPO by a three-step procedure. Since the phosphorus and the adjacent aliphatic carbon are both chiral centers, two pairs of enantiomers exist in 3a, 3b, or 3c. Compound 3a′, which is a pair of enantiomers existing in 3a, was isolated using recrystallization in ethyl acetate solvent. All the structures were confirmed by FT-IR, NMR, and MS spectra. The X-ray analysis indicated that the 3a′ is the RR/SS enantiomers and belongs to the monoclinic crystal system, its space group being P2₁/c. The thermal properties were investigated by DSC and TG. It has been found that the peak temperature of thermally induced ring-opening reaction was around 260–270 °C. Compounds (3a–3c, 3a′, and 3c′) had two similar thermal processes from 50 to 600 °C in TG, whereas the compound 3b′ had three thermal processes. The char yields of 3a–3c were 18.10, 16.84, and 16.34 %, respectively, while those of 3a′–3c′ were 26.00, 31.80, and 19.21 %, respectively. The results indicated that compounds 3a′–3c′ had better char properties than 3a–3c.     

Sterically hindered inversion of nitrogen atoms in cyclic hydrazines:N,N′-dialkyl-1,3,4-oxadiazolidines; 1,3,4-thiadiazolidine; and 4,5-benzo-1,2,3,6-tetrahydropyridazine

N,N′-Diisopropyl-substituted 1,3,4-oxadiazolidine3c, 1,3,4-thiadiazolidine6, 4,5-benzo-1,2,3,6-tetrahydropyridazine8, and new 3,4-dialkyl-1,3,4-oxadiazolidines9–14 were synthesized and studied. The configurational stability of the N atoms does not change on going from compound3c to itsS-analog6 and decreases in the case of pyridazine8. 3,4-Di-tert-alkyl-1,3,4-oxadiazolidines3d and11–14 were found to be promising objectes for optical resolution.     

Syntheses and antibacterial studies of some 2-[5-(Aryl)-[1,3,4]oxadiazole-2-ylsulfanyl] alkanoic Acids

Some new 2-[5-(aryl)-[1,3,4]oxadiazole-2-ylsulfanyl]alkanoic acids were synthesized and studied for their antibacterial activity. These compounds were prepared from aromatic carboxylic acid hydrazides. Aromatic carboxylic acid hydrazides 1 on refluxing with carbon disulfide and methanolic potassium hydroxide and then on subsequent acidification with hydrochloric acid furnish 5-aryl-1,3,4-oxadiazole-2-thiones 2. 2-Chloro alkanoic acids react with 2 in alkaline media and on acidification yield the title compounds 3. These compounds were characterised by CHN analyses, IR, mass and ¹H NMR spectral data. All the compounds were evaluated for their in vitro antibacterial activity against two Gram negative strains (Escherichia coli and Pseudomonas aeruginosa) and two Gram positive strains (Bacillus subtilis and Staphylococcus aureus) and their minimum inhibitory concentration (MIC) were determined.     

A convenient, rapid and eco-friendly synthesis of isoxazoline heterocyclic moiety containing bridge at 2°-amine as potential pharmacological agent

2-Amino-4-(coumarin-3-yl)-thiazole (1) reacted with acetyl chloride gives compound (2) which on further refluxed with various aromatic aldehydes gives compound (3a-j). Thus obtained (3a-j) on further condensed with NH₄OH.HCl using NaOH as a catalyst afforded isoxazoles (4a-j). All the synthesized compounds characterized on the basis of the IR, ¹H NMR, ¹³C NMR and elemental analysis. All the compounds have been screened for antibacterial activity against bacteria (Gram + ve) & (Gram ? ve) and antifungal activity.     

Synthesis and characterization of a series of chiral NHC–Pd complexes derived from l-phenylalanine

The synthesis of a series of chiral Pd(L)PyBr₂ (3a–3e) and Pd(L)PyCl₂ (4d and 4e) complexes from l-phenylalanine is presented (L = (S)-3-allyl-4-benzyl-1-(2,6-diisopropylphenyl)-imidazolin-2-ylidene (a), (S)-4-benzyl-1-(2,6-diisopropylphenyl)-3-(naphthalen-2-ylmethyl)imidazolin-2-ylidene (b), (S)-4-benzyl-3-(biphenyl-4-ylmethyl)-1-(2,6-diisopropylphenyl)imidazolin-2-ylidene (c), (S)-4-benzyl-1-(2,6-diisopropylphenyl)-3-(naphthalen-1-ylmethyl)imidazolin-2-ylidene (d) or (S)-4-benzyl-1-(2,6-diisopropylphenyl)-3-(2,4,6-trimethylbenzyl)imidazolin-2-ylidene (e). The complexes were characterized by physicochemical and spectroscopic methods, and the X-ray crystal structures of 3a–3c and 4d are reported. In each case, there is a slightly distorted square-planar geometry around palladium, which is surrounded by imidazolylidene, two trans halide ligands and a pyridine ligand. There are π–π stacking interactions in the crystal structures of these complexes. Complex 3a showed good catalytic activity in the Cu-free Sonogashira coupling reaction under aerobic conditions.     

The synthesis of some new imidazole and triazole derivatives: crystal Structure and DFT-TDDFT investigation on electronic structure

A series of new N′-3-(1H-imidazol-1-yl)propylcarbamoyl-4-halogenebenzo hydrazonate (3a–b) were obtained by reaction Ethyl 2-((4-halogene phenyl) (ethoxy) methylene) hydrazinecarboxylate (1) and N-(3-aminopropyl)imidazole (2) at 120–140 °C. Compounds (4a–b) were obtained by the reaction compound 1 and N-(3-aminopropyl)imidazole (2) at 160–180 °C. The structures of compounds 3,4 have been inferred through UV–Vis, IR, ¹H/¹³C NMR, mass spectrometry, elemental analyses, and X-ray crystallography. DFT level 6-31G (d) calculations provided structural information. The electronic structure of compound 3a has been studied by DFT level 6-31G (d) calculations using the X-ray data. The results are accordance with X-ray data.     

Study of cis–trans stereochemistry of 2-(2-chlorobenzylideneamino)phenol and 2-(2-chlorophenyl imino)methyl)phenol (Schiff bases) by GC and GC-MS spectrometry

Cis–trans stereochemistry of 2-(2-chlorobenzylideneamino)phenol (1) and 2-(2-chlorophenyl imino)methyl)phenol (2) (Schiff bases) was studied by GC-MS spectrometry, and cis–trans conversion of the two compounds in solution was investigated by GC. Thus, 2 exists as a sole trans configuration and its conversion to cis was unsuccessful in any circumstance, while compound 1 exists as a mixture of two configurations in solution, occurrence of which were dependent on the temperature, heating time, solvent, and acid catalyst. X-ray crystallography of solid 1 presented a sole trans configuration.     

A study on thermal behaviors of mono ethyl ester azocalix[4]arene derivatives

In the present study, thermal stabilities of five new family of azocalix[4]arene mono ethyl ester derivatives, 4a–e, were investigated using thermogravimetry, differential thermogravimetry, and differential thermal analysis methods. It was found that all compounds showed thermal stability up to 236 °C averagely. After this temperature, decomposition of compounds starts gradually. The decomposition routes of 4a–c compounds are similar and occur with two stages. Ester alkyl groups decompose and remove from the structure in the first stage. Second stage corresponds to rest of structure decomposition. The decomposition routes of the 4d–e compounds are different from the decomposition routes of the 4a–c compounds. These compounds include halogen, and decomposition reactions realize with three and four stages respectively.     

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.     

Guest inclusion in cyclic imides containing flexible tethers

Guest inclusion properties of two cyclic imides which have carboxylic acids connected through flexible tether, namely, 4-(1,3-dioxo-1,3-dihydro-isoindol-2-ylmethyl)-cyclohexanecarboxylic acid (1) and 4-(1,3-dioxo-1H,3H-benzo[de]isoquinolin-2-ylmethyl)-cyclohexanecarboxylic acid (2) are studied. The crystals of host 1 containing one molecule of 1, the crystals of 4,4′-bipyridine (bpy) cocrystal of 1 containing one molecule of 1 and half molecule of bpy (1a), the crystals of 1,4-dioxane solvate of 1 containing two molecule of 1 and one and half molecule of 1,4-dioxane (1b) and the crystals of quinoline solvate of 1 containing one molecule of 1 and one molecule of quinoline (1c) in their crystallographic asymmetric units are investigated. Intermolecular hydrogen bonded two dimensional (2D) sheet structure of 1 and 3D channel network of 1b are comprised of cyclic R ₂ ² (8) hydrogen bond motifs; whereas cleavage of dimeric carboxylic acid R ₂ ² (8) motifs occurs in the structures of 1a and 1c in which 3D host–guest networks are comprised of discrete O–H···N and cyclic R ₂ ² (7) interactions, respectively. Various types of weak interactions between the two symmetry nonequivalent host molecule are found to be responsible for the formation of channels (14 × 11 Å) filled by guest 1,4-dioxane molecules in the crystal lattice of 1b. Two different solvates of 2 containing one molecule of 2 with a water molecule (2a) and one molecule of 2 with a quinoline molecule (2b) in their crystallographic asymmetric units, respectively, are also crystallized in different space groups. The quinoline molecules are held with host molecules by discrete O–H···N and C–H···O interactions and reside inside the voids formed by 3D repeated hexameric assemblies of host molecules in the crystal lattice of 2b.     

Synthesis and in vitro and in vivo antitumor/anticancer activity of novel O-Mannich bases of 4,6-diaryl-3,4-dihydropyrimidine-2(1H)-ones

A new series of [4,6 substituted diaryl-1,6-dihydropyrimidin-2-yl-oxymethyl]-amines 5a–o have been synthesized by the Mannich condensation on the respective 4,6-diaryl-3,4-dihydropyrimidine-2(1H)-ones 4, in basic medium using formaldehyde along with three secondary amines, viz., dimethylamine, piperidine and morpholine. The dihydropyrimidinones 4 in turn were synthesized by the cyclocondensation of chalcones 3 with urea. Alternatively, compounds 4 were also prepared directly by one-pot 3-component cyclocondensation reaction starting from acetophenone, benzaldehyde and urea. The structures of all the newly synthesized compounds have been confirmed by their spectral and analytical data. All the O-Mannich bases 5 have been evaluated for their in vitro cytotoxic and antitumor activities, and based on the results, the potent compounds were selected for in vivo activity, as well. Only one compound 5m of the series has been found to be relatively more effective.     

Tribromogermyl monochelates — derivatives of N,N-disubstituted 2-hydroxycarboxylic amides

Reactions of GeBr₄ with N,N-dimethyl-2-trimethylsiloxypropionamide (2a), (S)-2-trime-thylsiloxypropionpyrrolidide ((S)-2b), and N,N-dimethyl-O-(trimethylsilyl)mandelamide (2c) afforded pentacoordinated neutral (O,O)-monochelates, viz., N,N-dimethyl-2-tribromoger-myloxypropionamide (3a), (S)-2-tribromogermyloxypropionpyrrolidide ((S)-3b), and N,N-dimethyl-O-(tribromogermyl)mandelamide (3c), respectively. X-ray diffraction study was performed for tribromides 3a, (S)-3b, and 3c, as well as for the N,N-dimethylmandelamide (1c) described earlier. According to the X-ray diffraction data, the Ge atom in tribromides 3a, (S)-3b, and 3c is pentacoordinated and has trigonal bipyramidal configuration with two halogen atoms and oxygen atom of the ether group in the equatorial positions and the halogen atom and the amide oxygen atom in the axial fragment, the bonds in which are somewhat longer as compared to the analogous bonds in tetracoordinated Ge compounds.     

New fluorochromatouranylates of alkali metals: Synthesis and structure

Four new fluorochromatouranylates, namely, K[UO₂(CrO₄)F] · 1.5H₂O (I), Rb[UO₂(CrO₄)F] · 1.5H₂O (II), Rb[UO₂(CrO₄)F] · 0.5H₂O (III), and Cs[UO₂(CrO₄)F] · 0.5H₂O (IV), have been synthesized, and their crystallographic characteristics have been determined. All the compounds crystallize in monoclinic system, space group P2₁/c, with the unit cell parameters a = 13.1744(5) Å, b = 9.4598(3) Å, c = 13.0710(4) Å, β = 103.746(1)°, Z = 4, R = 0.0235 (I); a = 13.5902(7) Å, b = 9.5022(4) Å, c = 13.2271(6) Å, β = 102.914(2)°, Z = 4, R = 0.0247 (II); a = 24.7724(8) Å, b = 12.6671(4) Å, c = 9.4464(3) Å, β = 97.661(1)°, Z = 8, R = 0.0448 (III); a = 25.725(1) Å, b = 12.8261(5) Å, c = 9.4929(4) β = 97.208(1)°, Z = 8 (IV). The pairs of compounds I and II and compounds III and IV are isostructural. Crystals of compounds I–III have been subjected to complete X-ray diffraction study. It has been established that the structures of compounds I–III are built of [UO₂(CrO₄)F] _n ^n? layers, which are parallel to the (100) plane and linked into a framework by alkali-metal cations located between layers, together with water molecules. The effect of topological and geometric isomerism on the structural features of 34 known uranyl compounds of the AT³M² crystallochemical group, to which the studied compounds I–III also belong, is discussed.     

Syntheses and extraction properties of novel biscalixarene and thiacalix[4]arene hydrazone derivatives

By reacting thiacalix[4]arene with p-tosyloxyethoxylbenzaldehyde 1, 3-bis(benzaldehyde-4-oxyethyloxy)-p-tert-butylthiacalix[4]arene (2) were prepared in yield of 65%. Refluxing compound 2 with aniline, salicylic hydrazide, nicotinic hydrazide and isonicotinic hydrazide, novel ringopening 1,3-bis-arylformyl-hydrazone substituted thiacalix[4]arene derivatives (3a–3d) were obtained in yields of 77–89%. Refluxing compound 2 with o-phenylendiamine, oxalyl dihydrazide, malonic dihydrazide and adipic dihydrazide in “1 + 1” intermolecular condensation mode under diluted condition, novel 1,3-bis-acyl hydrazone-bridged calix[4]arene derivatives (4a–4d) were prepared in good yields. Moreover, by condensating compound 2 with 1,3-bis(hydrazinocarbonyl-methoxy)-p-tert-butylcalix[4]arene (5), the first example of hydrazone-bridged biscalixarene (6) with calix[4]arene and thiacalix[4]arene subunits was facilely synthesized in yield of 90%. The noncompetitive and competitive extracting experiments showed that these novel hosts were good receptors for both metal cations and α-amino acids. Compounds 3a–3d and 4a–4d showed similar binding properties with high extraction percentage but low extracting selectivities. Biscalixarene 6 exhibited not only high extracting abilities but also good extracting selectivities.     

Über cyclische Guanidin—Mesityloxid- und Guanidin—Phoron-Kondensate

The basic product synthesized byTraube andSchwarz from mesityl oxide and guanidine has not been 4.4.6-trimethyl-4.5-dihydro-2-pyrimidinamine (1), but a mixture containing the 4.4.6-trimethyl-3.4-dihydro-2(1H)-pyrimidinimine (resp. an isomeric pyrimidinamine)2 a (resp.2 b, 2 c) and the dimeric 4.4′-methylenedi[2(1H)-pyrimidinimine] (resp. an isomeric methylenedipyrimidinamine)3 a (resp.3 b, 2 c) and the dimerisation reaction were studied in a series of experiments. The product of the reaction of guanidine and phorone is not the guanidinopropylpyrimidine8 ⁴, but the 4.4′-spirobi[2(1H)-pyrimidinimine] (resp. a spirobipyrimidinamine)11 a (resp.11 b, 11 c). No determination was possible on the basis of NMR whether the condensation products of guanidine—in solutions ofDMSO-d₆—are pyrimidinimines (2 a, 3 a, 11 a) or pyrimidinamines (2 b resp.2 c, 3 b resp.3 c, 11 b resp.11 c) or mixtures of the isomeric compounds. The NMR-and mass spectra of2 a (resp.2 b, 2 c),3 a (resp.3 b, 3 c),11 a (resp.11 b, 11 c) and their derivates are discussed.     

Synthesis and properties of novel stilbene-twelve alkyl quaternary ammonium salts as antibacterial optical whitening agents

Four novel stilbene-twelve alkyl quaternary ammonium salts 5a–d were synthesized. All synthesized compounds were characterized by FT-IR, ¹H-NMR and elemental analysis. Compounds 5a–d showed efficient whitening effect on cotton fiber and high fastness. Furthermore, compound 5c showed better stability to light than C186 in aqueous solution. The preliminary biological experiment demonstrated compounds 5a–d possessed significant antibacterial activities. Among them, compound 5d turned out to be the most active compound against Candida albicans with MIC₅₀ 4 μg/mL as well as E. coli with MIC₅₀ 16 μg/mL.     

Synthesis and biological evaluation of novel triazole substituted pyrazolyl-methylenehydrazinyl-5-arylidene thiazolidinone derivatives as antibacterial and cytotoxic agents

Novel triazole substituted pyrazolyl-methylenehydrazinyl-5-arylidene thiazolidinone derivatives 6a–n and 7a–l were synthesized and characterized by Fourier transform infrared, ¹H and ¹³C nuclear magnetic resonance, mass spectrometry and elemental (CHN) analysis. The in vitro antibacterial (6a–n and 7a–l) and cytotoxic (6a–n) activities were evaluated for these compounds. The results revealed that the compounds 6b, 6i, 6k, 7b, 7h displayed good antibacterial activity. The compounds 6c (IC₅₀ = 5.4 μM), 6l (IC₅₀ = 6.3 μM) and 6f (IC₅₀ = 9.85 μM) were effective for inhibition of human breast cancer cell line MCF-7. Similarly, the compounds 6b (IC₅₀ = 8.7 μM) and 6c (IC₅₀ = 9.06 μM) were shown to have effective inhibition on human cervical cancer cell line Hela.     

Two efficient methods for the synthesis of novel indole-based chalcone derivatives

Two powerful methods for the synthesis of indole-based chalcone derivatives, namely (E)-1-(2-chloro-1-(4-chlorobenzyl)-1H-indol-3-yl)-3-aryl(hetaryl)prop-2-en-1-ones (3a–l), are described, involving the ultrasound-assisted or solvent-free Claisen–Schmidt condensation reaction of 3-acetyl-2-chloro-1-(4-chlorobenzyl)indole (1) and various aromatic aldehydes (2a–l). The ultrasound-assisted Claisen–Schmidt condensation reaction was carried out using 1,4-dioxane as solvent and KOH as base at room temperature to give the corresponding products (3a–l) in yields ranging from 75 to 88 %. Alternatively, the Claisen–Schmidt condensation reaction could also be conducted under solvent-free conditions to obtain the products (3a–l) in comparable yields. The two procedures offer easy access to indole-based chalcone derivatives in short reaction times and good yields under mild conditions. Particularly, the advantageous aspect of the solvent-free method could avoid the use of environmentally hazardous and toxic solvents, and also reduced costs. The structures of all the newly synthesized indole-based chalcones 3a–l were confirmed by spectral data and elemental analyses.     

Two palladium(II) complexes based on Schiff base ligands: synthesis, characterization, luminescence, and catalytic activity

Two Pd(II) complexes involving Schiff base ligands, namely, [Pd(L1)₂] (1), [Pd₂(L₂)Cl₂] (2) [HL1 = 2-((2,6-diisopropylphenylimino)methyl)-4,6-dibromophenol, L2 = N-(4-isopropylbenzylidene)-2,6-diisopropylbenzenamine] have been synthesized using solvothermal methods and characterized by elemental analysis, IR-spectroscopy, thermogravimetric analysis, powder X-ray diffraction, UV–vis absorption spectra, and single-crystal X-ray diffraction. Complex 1 is a mononuclear cyclometalated Pd(II) complex, whereas complex 2 is a μ-chloro-bridged dinuclear. Both 1 and 2 display photoluminescence in the solid state at 298 K and possess fluorescence lifetimes (τ ₁ = 86.40 ns, τ ₂ = 196.21 ns, τ ₃ = 1,923.31 ns at 768 nm for 1, τ ₁ = 69.92 ns, τ ₂ = 136.40 ns, τ ₃ = 1,714.26 ns at 570 nm for 2). The Suzuki reactions of 4-bromotoluene with phenylboronic acid by complexes 1–2 have also been studied.     

Syntheses and characterization of a new class of vanadia precursors of oxime-modified oxovanadium(V) isopropoxide,crystal and molecular structure of [VO{ONC10H16}3]

Modification of [VO(OPrⁱ)₃] with oximes in different molar ratios, yielded new class of vanadia precursors, [VO{OPrⁱ}_3?n{L}_n] {where, n = 1–3 and LH = C₉H₁₆C=NOH (1–3) and (CH₃)₂C=NOH (4–6)}.All the products are yellow in colour. (1) and (2) are liquid/viscous liquid, while others are solids. Molecular weight measurements of all these derivatives and the ESI-mass spectral studies of (1), (2), (3) and (5) indicate their monomeric nature. ¹H and ¹³C{¹H} NMR spectra suggest that the oximato moieties are monodentate in solution which was further confirmed by the ⁵¹V NMR signals, appeared in the region expected for tetra-coordinated oxo-vanadium atoms. On ageing, a disproportionation reaction occurs in (1) and some crystals appeared. Single crystal X-ray diffraction analyses of the crystals obtained from (1) as well as from (3) were found to be the same and indicate the presence of side-on {dihapto η ²-(N, O)} binding modes of the oximato ligands, leading to the formation of seven coordination environment around the vanadium atom. Thermogravimetric curve of (1) exhibits multi-step decomposition with the formation of V₂O₅ as the final product at ~850 °C. Sol–gel transformation of (3) yielded (a) VO₂ sintered at 300 °C and (b) V₂O₅ at 600 °C. Similarly, sol–gel transformations of (1) and (2) yielded V₂O₅ (c) and (d) at 600 °C, respectively. Formation of monoclinic phase in (a) and orthorhombic phase in (b), (c) and (d) were confirmed by powder XRD patterns.