Cyclohexyl Group Research Articles

Copper-diphosphine complex catalysts for N-formylation of amines under 1 atm of carbon dioxide with polymethylhydrosiloxane

N-formylation of a wide range of amines proceeded using copper-diphosphine complexes as homogeneous catalysts with polymethylhydrosiloxane (PMHS) under 1 atm of CO2. In the reaction of piperidine, for example, the turnover number (TON) reached 11 700 in 23 h with 90% yield of the formylated product. This TON value is much higher than those of the reported catalysts for the formylation of amines under 1 atm of CO2 with hydrosilanes. The Cu complexes with phosphines having ortho-phenylene structures acted as good ligands for the formylation, as compared to a bidentate ligand connected with a propyl chain and a monodentate ligand. Among these diphosphines, ligands with alkyl functionalities, such as isopropyl and cyclohexyl groups, produced better results than the phenyl group. Not only cyclic secondary amines, but also linear secondary amines and aromatic and aliphatic primary amines were found to be reactive substrates. In the case of 2,2,6,6-tetramethylpiperidin-4-amine, the formylation proceeded regioselectively. A catalytic reaction pathway was proposed from a separate experiment using [Me2NCO2][Me2NH2].

A Z′ = 6 crystal structure of (E)-N,N′-dicyclohexylacetamidine

The crystal and molecular structure of (E)-N,N′-dicyclohexylacetamidine (1) is described. Crystalline material of 1 was obtained by sublimation. Single-crystal X-ray analysis revealed a centrosymmetric triclinic structure (space group P1¯) with six molecules in the asymmetric unit (Z′=6). The six crystallographically distinct molecules all exhibit an E-syn structure, but differ in the orientation of the cyclohexyl groups about the central acetamidine moiety. In the crystal, the molecules form polymeric helices via NH⋯N hydrogen bonds. The crystal structure comprises two crystallographically distinct helices of opposite handedness (P and M form). The characterisation of 1 in the solid-state is augmented by powder X-ray diffraction, infrared spectroscopy and thermal analysis. Density functional theory (DFT) structure optimisation and frequency calculation were performed at the B3LYP/cc-pVTZ level. The DFT results for the isolated molecule are compared with the experimental results for the solid-state.

Tetrabromidobis(dicyclohexylphosphane-κP)digallium(Ga—Ga)

The title compound, a GaII dimer, [Ga2Br4(C12H23P)2], was synthesized by reaction of GaBr(THF)n (THF is tetra­hydro­furan) with dicyclo­hexyl­phosphine in toluene. At 150 K the crystallographically centrosymmetric molecule exhibits disorder in which one of the two independent cyclo­hexyl groups is modelled over two sites in a 62 (1):38 (1) ratio. In d 6-benzene solution, the compound exhibits virtual C 2h symmetry as determined by 1H NMR. The coordination environment of the GaII atom is distorted tetrahedral.

Can Functionalized Cucurbituril Bind Actinyl Cations Efficiently? A Density Functional Theory Based Investigation

The feasibility of using cucurbituril host molecule as a probable actinyl cation binders candidate is investigated through density functional theory based calculations. Various possible binding sites of the cucurbit[5]uril host molecule to uranyl are analyzed and based on the binding energy evaluations, μ(5)-binding is predicted to be favored. For this coordination, the structure, vibrational spectra, and binding energies are evaluated for the binding of three actinyls in hexa-valent and penta-valent oxidation states with functionalized cucurbiturils. Functionalizing cucurbituril with methyl and cyclohexyl groups increases the binding affinities of actinyls, whereas fluorination decreases the binding affinities as compared to the native host molecule. Surprisingly hydroxylation of the host molecule does not distinguish the oxidation state of the three actinyls.

Effects of Cyclic-Hydrocarbon Substituents and Linker Length on Physicochemical Properties and Reorientational Dynamics of Imidazolium-Based Ionic Liquids

We synthesized a series of alkylimidazolium-based ionic liquids (ILs) incorporating cyclopentyl, cyclohexyl, or phenyl groups as nonionic units substituted on an acyclic alkyl linker and characterized them with respect to physicochemical properties and reorientational dynamics. The effects of the nonionic substituents and linker length on the properties of these ILs were carefully examined. The physicochemical properties of the ILs are found to partially reflect the properties of the nonionic substituents. While the liquid densities showed a similar trend in linker-length dependence of each series of ILs, a distinct trend was observed for the shear viscosities of them. By comparison of correlation times obtained by (13)C NMR spectroscopy, it is revealed that elongation of the linkers influences the characteristic effects of the nonionic substituents on the reorientational dynamics of the system.

Comparison between Cycloalkyl- and n-Alkyl-Substituted Imidazolium-Based Ionic Liquids in Physicochemical Properties and Reorientational Dynamics

We synthesized three series of imidazolium-based ionic liquids (ILs) containing cycloalkyl groups such as cyclopentyl, cyclohexyl, or cycloheptyl groups incorporating bis(trifluoromethanesulfonyl)amide anions and characterized them with respect to physicochemical properties and molecular reorientational dynamics. A comparison of the physicochemical properties revealed that cycloalkyl-substituted imidazolium ILs have higher densities, viscosities, and glass transition temperatures than the respective n-alkyl-substituted imidazolium ILs. Among three series, the cyclopentyl-substituted IL exhibits exceptionally lower viscosity. Observation of correlation times by (13)C NMR spectroscopy revealed that a remarkably lower viscosity for the cyclopentyl-substituted IL and a considerably higher viscosity for the cyclohexyl- and cycloheptyl-substituted ones are closely related to the respective reorientational motion of the cations. The cause of these distinctions is suggested to be attributed to the difference of activation energy for the conformational interconversion of their substituents.

Molecular dynamics simulation studies of betulinic acid with human serum albumin

Betulinic acid (BA) is a naturally occurring pentacyclictriterpenoid possessing anti-retroviral, anti-cancer, and anti-inflammatory properties. Here, we studied the interaction of BA with human serum albumin (HSA) by using molecular docking, and molecular dynamic simulation methods. Molecular docking studies revealed that BA can bind in the large hydrophobic cavity of drug binding site I of sub-domain IIA and IIB, mainly by the hydrophobic interactions and also by hydrogen bond interactions. In which several cyclohexyl groups of BA are interacting with Phe(206), Arg(209), Ala(210), Ala(213), Leu(327), Gly(328), Leu(331), Ala(350), and Lys(351), residues of sub-domain IIA and IIB of HSA by hydrophobic interactions. Also, hydrogen bond interactions were observed between the hydroxyl (OH) group of BA with Phe(206) and Glu(354) of HSA, with hydrogen bond distances of 0.24 nm,0.28 nm respectively. Further, specifically, the molecular dynamics study makes an important contribution in understanding the effect of the binding of BA on conformational changes of HSA and the stability of the protein-drug complex system in aqueous solution. The root mean square deviation values of atoms in the free HSA molecule were calculated from 3000 ps to 5000 ps trajectory and the results were obtained as 0.72 ± 0.036 nm and 0.81 ± 0.032 nm for free HSA and HSA-BA, respectively. The radius of gyration (Rg) values of both unliganded HSA and HSA-BA were stabilized at 2.59 ± 0.03 nm, 2.51 ± 0.01 nm, respectively. Thus, this work may play an important role in the design of new BA inspired drugs with desired HSA binding affinity.

Molecular Determinants of Ligand Binding Modes in the Histamine H4 Receptor: Linking Ligand-Based Three-Dimensional Quantitative Structure–Activity Relationship (3D-QSAR) Models to in Silico Guided Receptor Mutagenesis Studies

The histamine H(4) receptor (H(4)R) is a G protein-coupled receptor (GPCR) that plays an important role in inflammation. Similar to the homologous histamine H(3) receptor (H(3)R), two acidic residues in the H(4)R binding pocket, D(3.32) and E(5.46), act as essential hydrogen bond acceptors of positively ionizable hydrogen bond donors in H(4)R ligands. Given the symmetric distribution of these complementary pharmacophore features in H(4)R and its ligands, different alternative ligand binding mode hypotheses have been proposed. The current study focuses on the elucidation of the molecular determinants of H(4)R-ligand binding modes by combining (3D) quantitative structure-activity relationship (QSAR), protein homology modeling, molecular dynamics simulations, and site-directed mutagenesis studies. We have designed and synthesized a series of clobenpropit (N-(4-chlorobenzyl)-S-[3-(4(5)-imidazolyl)propyl]isothiourea) derivatives to investigate H(4)R-ligand interactions and ligand binding orientations. Interestingly, our studies indicate that clobenpropit (2) itself can bind to H(4)R in two distinct binding modes, while the addition of a cyclohexyl group to the clobenpropit isothiourea moiety allows VUF5228 (5) to adopt only one specific binding mode in the H(4)R binding pocket. Our ligand-steered, experimentally supported protein modeling method gives new insights into ligand recognition by H(4)R and can be used as a general approach to elucidate the structure of protein-ligand complexes.

Modification to degradation of hexazinone in forest soils amended with sewage sludge

Influences of one sewage sludge on degradation of hexazinone and formation of its major metabolites were investigated in four forest soils (A, B, C and D), collected in Zhejiang Province, China. In non-amended forest soils, the degradation half-life of hexazinone was 21.4, 30.4, 19.4 and 32.8 days in forest soil A, B, C and D, respectively. Degradation could start in soil A and C without lag period because the two soils had been contaminated by this herbicide for a long time, possibly leading to completion of acclimation period of hexazinone-degrading bacteria. In forest soils amended with sewage sludge, the degradation rate constant increased by 17.3% in soil A, 48.2% in soil B, 8.1% in soil C and 51.6% in soil D, respectively. The higher degradation rates (soil A and C) in non-amended soils accord with the lower rate increase in sewage sludge-amended soils. Under non-sterile conditions, biological mechanism accounted for 51.8–62.4% of hexazinone degradation in four soils. Under sterile conditions, the four soils had the similar chemical degradation capacity for hexazinone. In non-amended soil B, only one metabolite (B) was detected, while two metabolites (B and C) were found in sewage sludge-amended soil B. Similarly situated in agricultural soils, N-demethylation at 6-position of triazine ring, hydroxylation at the 4-positon of cyclohexyl group, and removal of the dimethylamino group with formation of a carbonyl group at 6-position of triazine ring appear to be the principal mechanism involved in hexazinone degradation in sewage sludge-amended forest soils. These data will improve understanding of the actual pollution risk as a result of forest soil fertilization with sewage sludge.

Size and chain length effects on structural behaviors of biphenylcyclohexane-based liquid crystal nanoclusters by a coarse-grained model

Size and chain length effects on structural behaviors of liquid crystal nanoclusters were examined by a coarse-grained model and the configurational-bias Monte Carlo (CBMC) simulation. The nanoclusters investigated in this study are composed of the biphenylcyclohexane-based BCH5H liquid crystal molecule and its derivatives. Results of the study show that the average energy decreases (i.e., more negative) as the cluster size (i.e., the number of molecules) increases. With the increasing cluster size, the equilibrium conformation of the nanocluster changes gradually from a pipe-like structure (for the smaller systems) to a ball-like cluster (for the larger systems). The order parameter of the system reduces with the transition of the equilibrium conformation. Regarding the chain length effect, the pipe-like equilibrium conformation (for the smaller systems) was observed more close to a pipe as the length of the tail alkyl chain of the derivatives extended. However, due to the flexibility of the tail alkyl chain, the pipe conformation of the system deflects slightly about its cyclohexyl group as the tail extends further.

Hydrothermal Synthesis, Crystal Structure, and Characterizations of Five New Lanthanide(III) Diphosphonates with a Layered Structure

AbstractFive new lanthanide(III) diphosphonates, namely, Ln[(HL)(H2O)]·H2O [Ln = La (1), Ce (2), Pr (3), Nd (4), Sm (5); H4L = C6H11N(CH2PO3H2)2] were synthesized under hydrothermal reaction conditions at 140 °C and structurally characterized by X‐ray single‐crystal diffraction, X‐ray powder diffraction, IR spectroscopy, elemental, and thermogravimetric analysis. Compounds 1–5 are isostructural and exhibit a 2D framework structure. The LnO8 polyhedra form 1D zigzag chains along the c axis by edge‐sharing, which are further interconnected by CPO3 tetrahedra through edge‐ and corner‐sharing to form a 2D layer in the ac plane. The cyclohexyl groups of the ligands are orientated toward the interlayer space.

Viscosity coefficients of nematic liquid crystals: II. Measurements of some nematic liquid crystals†

Oscillating plate and rotational viscosity measurements are reported for a series of liquid crystals and include n-p-cyano-p-hexylbiphenyl (K18), 4-n-hepthyl-4′-cyanobiphenyl (K21), ethyl-cyclohexyl-ethyl-6-fluoro – n-propyl-biphenyl (I32), n-propyl-cyclohexyl-ethyl-6-fluoro – n-butyl-biphenyl (I43) and a n-pentyl-cyclohexyl-cyanophenyl : n-heptyl-cyclohexyl-cyanophenyl mixture. Rotational viscosity measurements were carried out over a temperature range from ambient to ∼90°C. Comparison of the values at a temperature of 5 K above the below the clearing point indicate an odd–even effect as the chain length of the hydrocarbon tail is altered. The principle viscosities η1, η2, η3 and η45were measured using an oscillating plate viscometer and the temperature dependences used to calculate the activation energies for flow in the various directions. The magnitude of the activation energy is shown to change with the length of the hydrocarbon chain. The incorporation of the cyclohexyl group imparts flexibility and reduces the activation energy flow, whilst the presence of the fluoro group increases the interactions between molecules, and this is reflected in higher values of the viscosity. The change of viscosity with alignment angle is explored for two of the systems studied and the fit to theory investigated. The Leslie–Ericksen coefficients are calculated for these systems and discussed in terms of changes in the molecular interactions.

5-Chloro-3-cyclohexylsulfinyl-2,7-dimethyl-1-benzofuran

In the title compound, C16H19ClO2S, the cyclo­hexyl ring adopts a chair conformation and the aryl­sulfinyl unit is positioned equatorial relative to the cyclo­hexyl group. The least-squares plane through all six C atoms of the cyclo­hexyl ring makes a dihedral angle of 74.80 (6)° with the mean plane of the benzofuran fragment. In the crystal, mol­ecules are linked through inter­molecular C—H⋯O hydrogen bonds.

Computational Study on the Mechanism and Selectivity of C–H Bond Activation and Dehydrogenative Functionalization in the Synthesis of Rhazinilam

The key platinum mediated C-H bond activation and functionalization steps in the synthesis of (-)-rhazinilam (Johnson, J. A.; Li, N.; Sames, D. J. Am. Chem. Soc. 2002, 124, 6900) were investigated using the M06 and B3LYP density functional approximation methods. This computational study reveals that ethyl group dehydrogenation begins with activation of a primary C-H bond in preference to a secondary C-H bond in an insertion/methane elimination pathway. The C-H activation step is found to be reversible while the methane elimination (reductive elimination) transition state controls rate and diastereoselectivity. The chiral oxazolinyl ligand induces ethyl group selectivity through stabilizing weak interactions between its phenyl group (or cyclohexyl group) and the carboxylate group. After C-H activation and methane elimination steps, Pt-C bond functionalization occurs through β-hydride elimination to give the alkene platinum hydride complex.

Propylene-vinylcyclohexane copolymers: Synthesis, properties, and oxidation of polymers

Propylene-vinylcyclohexane copolymers containing 0.02–0.37 mol % vinylcyclohexane are synthesized and characterized; the copolymers are prepared via bulk copolymerization at 60°C in the presence of a metallocene catalyst with the C2 symmetry rac-dimethylsilylidene-bis(2-methyl-4-phenylindenyl)zirconium dichloride activated by polymethylaluminoxane. The reactivity ratios are calculated to be 26.6 for propylene and 0.025 for vinylcyclohexane. The introduction of vinylcyclohexane into PP slightly affects the stereoregularity of the polymer chain but markedly decreases its molecular mass and changes the thermophysical and mechanical characteristics of the polymer. The oxidation characteristics of the prepared copolymers are estimated: The induction period of oxidation is determined from oxygen absorption, and the termination-rate constants of peroxide macroradicals is determined from the chemiluminescence of copolymers. The dependence of the kinetic characteristics of oxidation of the copolymers on the content of side cyclohexyl groups is found, and the possible mechanisms of oxidation of copolymers are considered.

3-Cyclopentylsulfonyl-5-fluoro-2-methyl-1-benzofuran

There are two independent mol­ecules, A and B, in the asymmetric unit of the title compound, C14H15FO3S, in each of which the cyclo­pentyl ring adopts an envelope conformation. The benzofuran units in each mol­ecule are essentially planar, with mean deviations from the least-squares plane defined by the nine constituent ring atoms of 0.009 (2) Å for mol­ecule A and 0.013 (2) Å for mol­ecule B. In the crystal, mol­ecules are linked by weak C—H⋯O hydrogen bonds. In the cyclo­pentyl ring of mol­ecule B, one C atom is disordered over two positions with site-occupancy factors of 0.60 (2) and 0.40 (2).

Effects of functional monomers on retention behavior of small and large molecules in monolithic capillary columns at isocratic and gradient conditions

The polarity of (poly)methacrylate monolithic capillary columns was varied by using alkylmethacrylate monomers with butyl, cyclohexyl, 2-ethylhexyl, lauryl, and stearyl functional groups in the polymerization mixture. The hydrodynamic properties, as well as the retention characteristics in RP-LC of small molecules (alkylbenzenes) and of proteins under gradient elution conditions were studied. The RP selectivity depends on the type of alkyl chain in methacrylate monomer; however, there was no direct correlation between the size of the monomer molecule and methylene or aromatic selectivity of the monlithic column. The lowest selectivity was found for column based on lauryl methacrylate monomer. On the other hand, butyl methacrylate column shows high phenyl selectivity and the column with stearyl methacrylate possesses the highest methylene selectivity for small molecules. The retention increases with longer alkyl chain in methacrylate monomer, especially for high molar mass proteins on all prepared columns and showed gradient elution behavior of proteins in agreement with the linear solvent strength gradient model. The poly(laurylmethacrylate) column showed lowest hydrophobicity but best efficiency for proteins of all columns tested.

Planar Chirality and Helical Polymers: Ferrocenyl-Substituted Amidinium–Carboxylate Salts

A series of amidinium–carboxylate salts, [FcC{N(Cy)H][O2CR′′] (Fc = ferrocenyl, R′′ = Me, tBu, Ph, mesityl, CF3) have been synthesized and structurally characterized. In each case, the amidinium cation forms two NH···O hydrogen bonds to carboxylate anions. The extent of aggregation is, however, dependent on the carboxylate substituent. For R′′ = Me, a 1:1 salt is observed with an {E,E}-configuration of cyclohexyl groups within the amidinium component, whereas R′′ = tBu forms a 2:2 dimeric salt with an {E,Z}-cation. This latter configuration generates a planar chiral cation. When R′′ = Ph or mesityl, the hydrogen-bonding forms a helical polymer, with each chain containing a single enantiomeric form of the cation. In contrast, when R′′ = CF3 the hydrogen-bonded polymer contains alternating enatiomeric forms of the cation.

Synthesis and Conformational Features of 4-(Cyclohexylsulfanyl)-1-(2,4-dinitrophenyl)-3-aryl-1H-pyrazole

A set of new 4-(cyclohexylsulfanyl)-1,3-diaryl-1H-pyrazoles has been synthesized using Vilsmeier's reagent. It is found that 4-(cyclohexylsulfanyl)-1-(2,4-dinitrophenyl)-3-(4-methoxyphenyl)-1H-pyrazole exists with the arylthio group in the equatorial position of the cyclohexyl group in solution, whereas it has the arylthio group in the axial position of the cyclohexyl group in crystal state as evidenced by NMR and single-crystal x-ray analysis respectively.

CH Activation versus Yttrium–Methyl Cation Formation from [Y(AlMe4)3] Induced by Cyclic Polynitrogen Bases: Solvent and Substituent‐Size Effects

The reaction of 1,3,5-triisopropyl-1,3,5-triazacyclohexane (TiPTAC) with [Y(AlMe(4))(3)] resulted in the formation of [(TiPTAC)Y(Me(3)AlCH(2)AlMe(3))(μ-MeAlMe(3))] by C-H activation and methane extrusion. In contrast, the presence of bulkier cyclohexyl groups on the nitrogen atoms in 1,3,5-tricyclohexyl-1,3,5-triazacyclohexane (TCyTAC) led to the formation of the cationic dimethyl complex [(TCyTAC)(2)YMe(2)][AlMe(4)]. The investigations reveal a dependency of the reaction mechanism on the steric bulk of the N-alkyl entity and the solvent employed. In toluene C-H activation was observed in reactions of [Y(AlMe(4))(3)] with 1,3,5-trimethyl-1,3,5-triazacyclohexane (TMTAC) and TiPTAC. In THF molecular dimethyl cations, such as [(TCyTAC)(2)YMe(2)][AlMe(4)], [(TMTAC)(2)YMe(2)][AlMe(4)] and [(TiPTAC)(2)YMe(2)][AlMe(4)], could be synthesised by addition of the triazacyclohexane at a later stage. The THF-solvated complex [YMe(2)(thf)(5)][AlMe(4)] could be isolated and represents an intermediate in these reactions. It shows that cationic methyl complexes of the rare-earth metals can be formed by donor-induced cleavage of the rare-earth-metal tetramethylaluminates. The compounds were characterised by single-crystal X-ray diffraction or multinuclear and variable-temperature NMR spectroscopy, as well as elemental analyses. Variable-temperature NMR spectroscopy illustrates the methyl group exchange processes between the cations and anions in solution.