Di(1H,1H,2H,2H-perfluorooctyl)-dibenzo-18-crown-6: A “light fluorous” recyclable phase transfer catalyst

A series of dibenzo-18-crown-6 lariat ethers containing two C₇H₁₅ (11), (CH₂)₂C₆F₁₃ (14), (CH₂)₂C₈F₁₇ (15), NHC₇H₁₅ (18) and NHCH₂C₆F₁₃ (19) sidearms were prepared and the single crystal X-ray structure of cis-4,4′-di(1H,1H,2H,2H-perfluorodecyl)-dibenzo-18-crown-6 (15a) is reported. The “light fluorous” dibenzo-18-crown-6 ether (14) has emerged as a stable and robust PTC catalyst, which can be recycled efficiently by fluorous solid-phase extraction, and gives better PTC catalytic activity compared to the parent, non-fluorinated PTC catalyst, dibenzo-18-crown-6, and the alkylated derivative (11) in aliphatic and aromatic nucleophilic substitutions.     

Structure of benzo- and dibenzocrown ethers and their H-bonded adducts. 4. Structural motifs in the 2,4-dithiouracil complexes with 4-bromo- and 4-nitrobenzo-18-crown-6, [2.4]dibenzo- and thia[1.5]dibenzo-18-crown-6

Four novel complexes of 2,4-dithiouracil (pyrimidine-2,4(1H,3H)-dithione, DTU) with 18-membered benzo- and dibenzo-crown ethers were synthesized in approximately the same conditions and studied by single crystal diffraction. Hydrogen bonding was observed to be the most important for the complexation in the solid state but π–π interactions also contribute to it. The crystalline monohydrates of the 1:1:1 stoichiometry are recorded for 4-bromo- and 4-nitrobenzo-18-crown-6 (complexes 1 and 2), while complexes with [2.4]dibenzo- and thia[1.5]dibenzo-18-crown-6 (complexes 3 and 4) represent anhydrous adducts of the 2:2 ratio. The crystal structures reveal three supramolecular structural motifs: the alternative chain for the ternary complex 1 and two types of capsules for complexes 2?4 where the DTU dimers are encapsulated inside the space restricted by two crown molecules.     

(Mesitylene)ruthenium π-complexes with benzo-15-crown-5 and dibenzo-18-crown-6

The reactions of benzo-15-crown-5 and dibenzo-18-crown-6 with 1 equiv. of [(mes)Ru(MeNO₂)₃]²⁺ (mes = 1,3,5-C₆H₃Me₃) give the mononuclear complexes [(mes)Ru(η⁶-benzo-15-crown-5)]²⁺ (1) and [(mes)Ru(η⁶-dibenzo-18-crown-6)]²⁺ (2) in 50% yield. Similar reaction with 2 equiv. of [(mes)Ru(MeNO₂)₃]²⁺ produces the dinuclear complex [(μ-η⁶:η⁶-dibenzo-18-crown-6)Ru₂(mes)₂]⁴⁺ (3) in 96% yield as a 2:3 mixture of cis- and trans-isomers. Structures of 2(OTf)₂ and trans-3(OTf)₄ were confirmed by X-ray diffraction. The NMR titration showed that mononuclear dications 1 and 2 bind Na⁺ ion less effective (K_a = 600 and 250 M^-1) than free benzo-15-crown-5 and dibenzo-18-crown-6 (K_a = 2 × 10⁵ and 5 × 10⁶ M⁻¹). The dinuclear tetracation 3 does not bind Na⁺ within measurable limits of NMR titration method. The electrochemical behaviour of complexes 1-3 was studied in propylene carbonate solution. They exhibit a partially chemically reversible Ru(II)/Ru(I) reduction, which in the case of the dinuclear complex 3 proceeds through two slightly separated steps. The redox activity of the complexes is substantially unaffected by the presence of sodium ion.     

Syntheses, spectroscopic characterization and metal ion binding properties of benzo-15-crown-5 derivatives and their sodium and nickel(II) complexes

New benzo-15-crown-5 derivatives containing nitro, amine and imine groups were prepared. Nitro compound (1) was prepared after the reaction?4′,5′-bis(bromethyl)benzo-15-crown-5 and o-nitrophenol in the presence of NaOH. After reduction process by using hydrazine hydrate and Pd/C amine compound (2) was formed. New crown ether imine compounds (3–5) were synthesized by the condensation of corresponding crown ether diamine (2) with salicylaldehyde derivatives. Sodium complexes of the crown compounds (1a–5a) form crystalline 1:1 (Na⁺: ligand) complexes with sodium perchlorate. Nickel(II) complexes (3b–5b) with 1:1 (Ni²⁺:ligand) stoichiometries were also been synthesized from the Schiff bases (3–5). The results indicated that the Schiff base ligands coordinated through the azomethine nitrogen and phenolic oxygen. The extraction ability of compounds (1, 3, 4 and 5) were also evaluated in chloroform by using several alkali and transition metal picrates such as Li⁺, Na⁺, K⁺, Cr³⁺, Mn²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Pb²⁺.     

Syntheses and spectroscopic characterization of double-armed benzo-15-crown-5 derivatives and their sodium and potassium complexes

A series of new benzo-15-crown-5 derivatives (1–6) containing formyl and imine groups were prepared. New formyl crown ethers (1 and 2) were prepared by reaction of 4′,5′-bis(bromomethyl)benzo-15-crown-5 with 2-hydroxy-3-methoxybenzaldehyde (o-vanillin) and 2-hydroxy-5-methoxybenzaldehyde in the presence of NaOH. New Schiff bases (3–6) were synthesized by the condensation of corresponding aldehydes with 1,3-diaminopropane and 1,4-diaminobutane. Sodium and potassium complexes (1a–6a and 1b–6b) of the crown compounds forming crystalline complexes of 1:1 (Na⁺:ligand) and 1:2 (K⁺:ligand) stoichiometries were also synthesized. The structures of the aldehydes 1 and 2, imines 3–6 and complexes (1a–3a and 1b–3b) were confirmed on the basis of elemental analyses, IR, ¹H- and ¹³C-NMR, and mass spectroscopy.     

Synthesis and fluorescence properties of 7-hydroxy-3-(2-pyridyl)coumarin derivatives

Three coumarin derivatives, 7-hydroxy-3-(2-pyridyl)coumarin (HPC), 7-(4-(5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl)benzyloxy)-3-(2-pyridyl)coumarin (Ox-PC), and 7-(4-(9H-carbazol-9-yl)butoxy)-3-(2-pyridyl)coumarin (Cz-PC), were synthesized and characterized by elemental analysis, ¹H NMR, FT-IR, and UV?Cvis absorption spectra. The fluorescence behaviors of the compounds in methanol solutions and solid states were investigated. HPC exhibits weak green emission, whereas Cz-PC and Ox-PC show strong blue emissions in dilute solutions.     

Isosteviol and some of its derivatives as receptors and carriers of amino acid picrates

The ability of diterpenoid isosteviol 1 (ent-16-oxobeyeran-19-oic acid) and some of its derivatives with ester and amide groups to bind amino acid picrates in the course of their transport through a liquid chloroform membrane was observed for the first time. Isosteviol was very competitive with dibenzo-18-crown-6 and N,N′-bis(isostevioyl)-1,4-phenylenediamine 5 was even more effective in transportation of d,l-tryptophan through a liquid chloroform membrane.     

Synthesis, Cation-Binding and Optical Spectral Studies of Photoemmitive Benzothiazole Crown Ethers

Crown ethers 1–4, encompassing a photoemittive benzothiazole chromophore have been synthesised using standard protocols. Alkali metal picrate extraction profiles reveal that compared to the known crown ethers, benzothiazole benzo-15-crown-5 1 and benzothiazole dibenzo-18-crown-6 3 exhibit relatively higher % extraction for K⁺ than Na⁺ ions. The UV-visible and fluorescence spectra of 1–4, in comparison to their neutral forms were found to be red shifted on protonation due to enhanced intramolecular charge transfer transition. The ortho-substituted benzothiazole crowns 2–4 showed higher Stokes shifts compared to the para analog 1 in the presence of CF₃CO₂H, presumably due to H-bond assisted conformational restriction. No changes were noticeable in the absorption spectra in the presence of alkali metal ions. Even, fluorescence properties of 1–4 were not found to be drastically perturbed by these ions. While 1 exhibited slight quenching at alkali metal ion concentration over 10-folds with respect to that of 1, interestingly, 2–4 showed a slight enhancement of fluorescent intensity at least up to 10-fold concentration of metal ions over those of 2–4. Further increase of metal ion concentrations produces quenching effects. This behavior has been tentatively explained by invoking electrostatic interaction between these cations and the benzothiazole nitrogen ligand.     

Solvent extraction of europium trifluoromethanesulfonate into nitrobenzene by using three electroneutral receptors

From extraction experiments and $ \gamma $ -activity measurements, the extraction constants corresponding to the general equilibrium Eu³⁺(aq) + 3 A^?(aq) + L(nb) $ \Leftrightarrow $ EuL³⁺(nb) + 3A^?(nb) taking place in the two-phase water–nitrobenzene system ( $ {\text{A}}^{ - } = {\text{CF}}_{ 3} {\text{SO}}_{3}^{ - } $ ; L = electroneutral receptors denoted by 1, 2, and 3 – see Scheme 1; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Further, the stability constants of the EuL³⁺ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the series of 3 < 2 < 1.

Synthesis of dibenzocrown ethers with pendant thioamide groups

The synthesis of eighteen crown ether compounds with pendant thioamide, N-alkylthioamide, and N,N-dialkylthioamide groups is reported. The new crown ether compounds are obtained by one-step reactions from the corresponding sym-dibenzo-16-crown-5-oxyacetamides and sym-(propyl)dibenzo-16-crown-5-oxyacetamides with Lawesson's reagent.     

Synthesis and characterization of glycol-modified vanadium(V) oxoisopropoxide and their oximato derivatives: sol–gel transformations of [VO(OPr i )3], [VO{OCH2CH2OCH2CH2O}{OPr i }] and [VO{OCH2CH2OCH2CH2O}{ON=C(CH3)(C4H3S-2)}] to vanadia

Reaction of [VO(OPr ⁱ )₃] (1) with [O(CH₂CH₂OH)₂] in 1:1 molar ratio in anhydrous benzene yield glycol-modified precursor, [VO{OCH₂CH₂OCH₂CH₂O}{OPr ⁱ }] (2). Further reactions of (2) with internally functionalized oximes in anhydrous benzene yield heteroleptic complexes of the type [VO{OCH₂CH₂OCH₂CH₂O}{ON=C(R)(Ar)}] (3–8) {where R=CH₃, Ar=C₄H₃O-2 (3), C₄H₃S-2 (4), C₅H₄N-2 (5); and when R=H, Ar=C₄H₃O-2 (6), C₄H₃S-2 (7), C₅H₄N-2 (8)}. All these derivatives have been characterized by elemental analyses, molecular weight measurements and spectroscopic techniques. The crysoscopic molecular weight measurement as well as FAB mass study suggests dimeric nature of (2). However, FAB mass spectrum of (4), and the crysoscopic molecular weight measurements of (3), (4), (5) and (6) indicate the monomeric behavior of the oximato derivatives (3–8). Hexa-coordination around vanadium(V) has been proposed for both monomeric and dimeric derivatives. Sol–gel transformations of (1), (2) or (4) to vanadia [(a), (b) or (c), respectively] have been carried out at low sintering temperature (600 °C). The XRD patterns of (a), (b) or (c) indicate formation of a single orthorhombic phase in all the three cases. The SEM images suggest grain like [for (a) and (b)] and rod like [for (c)] morphology of the crystallites. IR, Raman spectra as well as EDX analyses indicate formation of pure vanadia. Absorption spectra of the vanadia (b) and (c) suggest energy band gaps of 2.53 and 2.65 eV, respectively.     

Cytotoxicity evaluation of coumarin derivatives containing 4-bromophenyl or anthracene moieties

The cytotoxic properties of four synthesized coumarin derivatives containing 4-bromophenyl or anthracene moieties against the human hepatocellular carcinoma cell lines (HepG-2) were investigated in vitro by use of the sulforhodamine B (SRB) assay. The four coumarin derivatives are 3-(4-bromophenyl)-benzo[5,6]coumarin (1a), 3-(4-bromophenyl)-7-(N,N-diethylamino)coumarin (1b), 3-(4-(anthracen-10-yl)phenyl)-benzo[5,6]coumarin (2a), and 3-(4-(anthracen-10-yl)phenyl)-7-(N,N-diethylamino)coumarin (2b). The preliminary results indicate that 1a, 2a, and 2b have significant cytotoxicity against HepG-2 whereas 1b has a growth-promotion effect.     

Synthesis and thermal behavior study of complexes of the type [Pd(μ-X)(4-eb-p-phen)]2 (X = Cl,Br, I,N3, NCO,SCN) and 4-eb-p-phen [bis(4-ethylbenzyl)p-phenylenediimine]

The Schiff base bis(4-ethylbenzyl) p-phenylenediimine, 4-eb-p-phen (1), and six new dimeric Pd(II) complexes of the type [Pd(μ-X)(4-eb-p-phen)]₂ {X = Cl (2), Br (3), I (4), N₃ (5), NCO (6), SCN (7)} have been synthesized and characterized by elemental analysis, IR spectroscopy, and ¹H and ¹³C{¹H}-NMR experiments. The thermal behavior of the complexes 2–7 has been investigated by means of thermogravimetry and differential thermal analysis. From the final decomposition temperatures, the thermal stability of the complexes can be ordered in the following sequence: 3 > 4 > 7 > 2 ≈ 5 > 6. The final products of the thermal decompositions were characterized as metallic palladium by X-ray powder diffraction (XRD).     

Amino(tert-butyl-NNO-azoxy)furoxans: synthesis, isomerization, and rearrangement of N-acetyl derivatives

3-Amino-4-(tert-butyl-NNO-azoxy)furoxan (1a) and 4-amino-3-(tert-butyl-NNO-azoxy)-furoxan (1b) and their acetyl derivatives 6a,b were obtained. The equilibria 1a ai 1b and 6a ? 6b were studied. Furoxan 6b can undergo thermal rearrangement into 3-[(tert-butyl-NNO-azoxy)(nitro)methyl]-5-methyl-1,2,4-oxadiazole (7), prolonged heating of which gives N-(2-tert-butyl-5-nitro-1-oxido-2H-1,2,3-triazol-4-yl)acetamide (8). With the transformation 7 → 8 as an example, the possibility of participation of the azoxy group in the Boulton-Katritzky rearrangements was demonstrated for the first time.     

Syntheses and crystal structures of (18-crown-6)bis(perchlorato-O,O′)strontium and (18-crown-6)bis(perchlorato-O,O′)barium

Two complexes, namely, (18-crown-6)bis(perchlorato-O,O′)strontium (I) and (18-crown-6)bis(perchlorato-O,O′)barium (II), are synthesized. Their crystal structures are determined by X-ray diffraction analysis. The structures of I (space group P2₁/c, a = 15.266 Å, b = 11.080 Å, c = 13.235 Å, β = 109.20°, Z = 4) and II (space group P2₁/n, a = 8.330 Å, b = 11.202 Å, c = 11.752 Å, β = 98.38°, Z = 2) are solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.077 (I) and 0.041 (II) against 3714 (I) and 2478 (II) independent reflections (CAD-4 diffractometer, λMoK _α radiation). Complex molecules [Sr(18C6)(ClO₄)₂] in the structure of I and [Ba(18C6)(ClO₄)₂] in II (in the inversion center)—are of the host-guest type. The Sr²⁺ or Ba²⁺ cation is localized in the center of a cavity of the 18-crown-6 ligand and coordinated by its all six O atoms. In compounds I and II, the coordination polyhedron of the Sr²⁺ and Ba²⁺ cations (coordination number 10) can be described as a distorted hexagonal bipyramid with two bifurcated vertices at two O atoms of two ClO ₄ ^? ligands, which are disordered in I and II and each of them has two orientations.     

Molecular geometry and electronic structures of stable organic derivatives of divalent germanium and tin [(\operatorname{Me} _3 \operatorname{Si} )_2 \operatorname{N} {\kern 1pt} ---{\kern 1pt} Me_2 ]_n (M = Ge, n = 1; M = Sn, n = 2): a theoretical study

The molecular geometry and electronic structure of stable organic derivatives of divalent germanium and tin, [(Me₃Si)₂N-M-OCH₂CH₂NMe₂]_n (M = Ge (4), n = 1; M = Sn (5), n =2) and their isomers with broken (4a, 5a) and closed (4b, 5b) intramolecular coordination bonds M←NMe₂, were studied by the density functional (PBE/TZ2P/SBK-JC) and NBO methods. Factors responsible for stability of their dimers 4c and 5c were established. Dimerization of 5b in the gas phase is a thermodynamically favorable process (ΔG ⁰ = ?2.1 kcal mol^?1) while that of 4b is thermally forbidden (ΔG ⁰ = 10.1 kcal mol^?1), which is consistent with experimental data. The M←NMe₂ coordination bond energies, ΔE ⁰, were found to be ?5.3 and ?8.6 kcal mol^?1 for M = Ge and Sn, respectively. NBO analysis showed that the metal atoms M in molecules 4 and 5 are weakly hybridized. The lone electron pairs of the M atoms have strong s-character while vacant orbitals of these atoms, LP* M, are represented exclusively by the metal np_z-AOs. The strongest orbital interactions between subunits in dimers 4c and 5c involve electron density donation from the lone electron pairs of oxygen atoms (LP O) to the LP* M orbitals.     

Synthesis and antiproliferative activity in vitro of new 2-aminobenzimidazole derivatives. Reaction of 2-arylideneaminobenzimidazole with selected nitriles containing active methylene group

A series of pyrimido[1,2-a]benzimidazole and α-cyanocinnamic acid derivatives have been synthesized in the reactions of Schiff bases 2–7 with selected nitriles containing an active methylene group: malononitrile 8–12, cyanoacetamide 13–16, benzyl cyanide 17–21, benzoylacetonitrile 22–24, cyanoacetate methyl ester 25–28 and benzylacetamide 29. The structures 8–29 were confirmed by the results of elementary analysis and their IR, ¹H-, ¹³C-NMR and MS spectra. The products 8–29 of various chemical structure pyrimido[1,2-a] benzimidazole 8–12, 14–16, 17–21, 23–24, 26 and α-cyanocinnamic acid derivatives 13, 22, 25, 27, 28 were obtained, which are of interest for biological studies or which can be substrates for further synthesis. The selected compounds 10, 13, 14, 17, 19, 21, 23–25 and 28 were screened for their antiproliferative activity in vitro against neoplastic and normal cell lines. The most active two compounds were: 2-(o-bromophenylene)-3-cyano-4-phenyl-1,2-dihydropyrimido[1,2-a]benzimidazole (24) and 3-cyano-4-phenyl-2-(2,4-dimethoxyphenyl)-1,2-dihydropyrimido[1,2-a]benzimidazole (23). However, similarly like cisplatin used as the control, they showed no selectivity towards cancer cells, by inhibiting proliferation of normal mouse fibroblasts in similar manner.      

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.     

1,2,4-Thiadiazol derivatives of cytisine alkaloid: solvate formation and phase transitions

1,2,4-Thiadiazol derivatives of cytisine alkaloid—N-(3-methylthio-1,2,4-thiadiazol-5-yl-aminocarbonylmethyl) (1), N-(3-ethylthio-1,2,4-thiadiazol-5-yl-aminocarbonylmethyl) (2), N-(3-hexylthio-1,2,4-thiadiazol-5-yl-aminocarbonylmethyl) (3) cytisine have been crystallized from different solvents and by X-ray and TG–DSC method were studied. By X-ray analysis the structures of the crystal solvate of 2 with dioxane have been determined. By topology represented solvate belongs to tabulate type. In the crystal structure two conformers of the host molecules were determined. By TG–DSC method has been shown, that methyl-, ethyl-, and hexyl cytisine derivatives can exist in two phase forms. But, unlike methyl- and ethyl-derivatives, hexyl-derivative of cytisine not form inclusion compounds.     

Diaquabromo(18-crown-6)rubidium and triaqua(18-crown-6)barium dibromide monohydrate: Synthesis and crystal structures

Two complexes are synthesized: diaquabromo(18-crown-6)rubidium [RbBr(18-crown-6)(H₂O)₂] (I) and triaqua(18-crown-6)barium dibromide monohydrate [Ba(18-crown-6)(H₂O)₃]²⁺ 2Br^? · H₂O (II). The orthorhombic structure of compound I (space group Pnma, a = 10.124 Å, b = 15.205 Å, c = 12.544 Å, Z = 4) and the monoclinic structure of compound II (space group C 2/c, a = 17.910 Å, b = 10.315 Å, c = 14.879 Å, β = 123.23°, Z = 4) are determined by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.063 (I) and 0.042 (II) for all 2293 (I) and 3363 (II) independent measured reflections (CAD-4 automated diffractometer, λMoK _α). The complex molecule [RbBr(18-crown-6)(H₂O)₂] in compound I and the randomly disordered cation [Ba(18-crown-6)(H₂O)₃]²⁺ in compound II are of the host-guest type: their Rb⁺ or Ba²⁺ cation (its coordination number is nine) is located in the cavity of the 18-crown-6 ligand and coordinated by all six O atoms. In structure I, the coordination polyhedron of Rb⁺ is a distorted hexagonal pyramid with a triple apex at the Br^? ligand and two O atoms of the water molecules. In structure II, the Ba²⁺ polyhedron is a distorted hexagonal bipyramid with one apex at the O atom of the water molecule and the other split apex at two O atoms of water molecules.