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In the title compound, ring conformations in the tetra­cyclic system are twist, chair, half-chair and boat-chair forms. In the crystal, the inter­molecular O—H⋯O hydrogen bonds connect the mol­ecules into a helical chain, and the inter­molecular C—H⋯O inter­actions link the chains into a three-dimensional architecture., In the fused tetra­cyclic system of the title compound, C29H36O9, the five-membered dioxolane ring adopts a twist conformation; the two adjacent C atoms deviate alternately from the mean plane of the other three atoms by −0.252 (6) and 0.340 (6) Å. The cyclo­hexane, cyclo­hexene and central cyclo­octane rings show chair, half-chair and boat-chair forms, respectively. There are three intra­molecular C—H⋯O inter­actions supporting the mol­ecular conformation, with one S(6) and two S(7) graph-set motifs. In the crystal, inter­molecular O—H⋯O hydrogen bonds connect the mol­ecules into a helical chain running along the c-axis direction, generating a C(7) graph-set motif. The chains are further linked by inter­molecular C—H⋯O inter­actions to construct a three-dimensional network. There is no valid C—H⋯π inter­action.

A gas chromatographic headspace analysis method was used to experimentally determine gas-to-liquid partition coefficients and infinite dilution activity coefficients for two saturated (2,2,4-trimethylpentane, cyclooctane) and 3 unsaturated hydrocarbons (1,7-octadiene, 1-hexyne, 4-vinyl-1-cyclohexene), one aromatic hydrocarbon (propylbenzene), one haloalkane (1,3-dichloropropane) and four halobenzenes (fluorobenzene, chlorobenzene, 1,2-dichlorobenzene, bromobenzene), two cyclic ethers (tetrahydrofuran, 1,4-dioxane), two alcohols (1-propanol, 2-propanol), three alkyl acetates (ethyl acetate, butyl acetate, pentyl acetate), and one alkanenitrile (acetonitrile) dissolved in 2-pyrrolidone at 298.15 K. The experimental results of the headspace chromatographic measurements, combined with published solubility and infinite dilution activity coefficient data, were used to derive Abraham model correlations for describing solute transfer into 2-pyrrolidone. Mathematical correlations based on the Abraham model describe the observed partition coefficient and activity coefficient data to within 0.14 log10 units (or less).

This study describes a time-dependent self-assembly generation of new copper(II) coordination compounds from an aqueous-medium reaction mixture composed of copper(II) nitrate, H3bes biobuffer (N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid), ammonium hydroxide, and benzenecarboxylic acid, namely, 4-methoxybenzoic (Hfmba) or 4-chlorobenzoic (Hfcba) acid. Two products were isolated from each reaction, namely, 1D coordination polymers [Cu3(μ3-OH)2(μ-fmba)2(fmba)2(H2O)2]n (1) or [Cu2(μ-OH)2(μ-fcba)2]n (2) and discrete tetracopper(II) rings [Cu4(μ-Hbes)3(μ-H2bes)(μ-fmba)]·2H2O (3) or [Cu4(μ-Hbes)3(μ-H2bes)(μ-fcba)]·4H2O (4), respectively. These four compounds were obtained as microcrystalline air-stable solids and characterized by standard methods, including the single-crystal X-ray diffraction. The structures of 1 and 2 feature distinct types of metal-organic chains driven by the μ3- or μ-OH- ligands along with the μ-benzenecarboxylate linkers. The structures of 3 and 4 disclose the chairlike Cu4 rings assembled from four μ-bridging and chelating aminoalcoholate ligands along with μ-benzenecarboxylate moieties playing a core-stabilizing role. Catalytic activity of 1-4 was investigated in two model reactions, namely, (a) the mild oxidation of saturated hydrocarbons with hydrogen peroxide to form alcohols and ketones and (b) the mild carboxylation of alkanes with carbon monoxide, water, and peroxodisulfate to generate carboxylic acids. Cyclohexane and propane were used as model cyclic and gaseous alkanes, while the substrate scope also included cyclopentane, cycloheptane, and cyclooctane. Different reaction parameters were investigated, including an effect of the acid cocatalyst and various selectivity parameters. The obtained total product yields (up to 34% based on C3H8 or up to 47% based on C6H12) in the carboxylation of propane and cyclohexane are remarkable taking into account an inertness of these saturated hydrocarbons and low reaction temperatures (50-60 °C). Apart from notable catalytic activity, this study showcases a novel time-dependent synthetic strategy for the self-assembly of two different Cu(II) compounds from the same reaction mixture.

A polymer of intrinsic microporosity (PIM) consisting of Tröger's base (TB) undergoes ring opening of the bicyclic amine upon N‐methylation followed by alkaline hydrolysis, resulting in a hybrid ladder polymer that contains diazacyclooctane (DACO) units with tert‐ and sec‐amino groups. The hybrid ladder polymers with various TB/DACO ratios can be prepared depending on the reaction conditions. Here we report a systematic study on the effect of DACO content on the thermal and gas adsorption properties of the hybrid ladder polymer. Using a PIM derived from 2,5‐diamino‐p‐xylene, we prepared hybrid ladder polymers with a DACO content ranging from 19% to 55% while having a similar molecular weight. The thermal stability of the hybrid ladder polymers, evaluated by thermogravimetric analysis, is decreased with the increase in DACO content. Based on gas adsorption measurements, the increase in DACO content results in the decrease in the BET surface area but improves the gas adsorption selectivity for CO2 against N2, likely due to high basicity of the sec‐amino group of DACO unit. This result demonstrates that the partial TB‐to‐DACO conversion of the TB‐based PIM may provide a simple but useful strategy to design polymer materials that enable selective CO2 capture and/or separation.

The synthesis and reactivity of the bimetallic rhodium–copper complex, Rh(COE)[P2N2]Cu, which is stabilized by the P2N2 macrocycle, is reported. In the solid state, the rhodium and copper centers are on opposite sides of the macrocyclic ring with the Cu(I) in a linear environment and the Rh(I) in a square planar array. However, in solution a very symmetrical structure is suggested on the basis of the 1H NMR data, which is consistent with at least two separate fluxional processes, rotation of the cyclooctene unit and movement of the Rh(I) unit between the two amido donors. Addition of H2 to Rh(COE)[P2N2]Cu results in the formation of ([P2N2H]RhH(μ-H)2Cu)2 via hydrogenation of the coordinated cyclooctene unit, oxidative addition of H2 to the rhodium center and hydrogenolysis of the copper amido unit. Monitoring the reaction of H2 by NMR spectroscopy indicated the formation of a number of intermediates which suggests hydrogenolysis of the copper amido linkage occurs to generate CuH in some form, along with Rh(COE)[P2N2H], which is converted to Rh(H)2[P2N2H] by hydrogenation of the cyclooctene, which then recombines with the CuH present to generate the final product. Deuteration studies indicate that there is considerable H/D scrambling in the cyclooctane produced that we attribute to reversible beta-elimination, migratory insertion steps.

Iron hexamesityl-5,15-diazaporphyrin was synthesized through the cross-coupling reaction of tetrabromodiazaporphyrin. The use of chloroiron(III) hexamesityl-5,15-diazaporphyrin as a catalyst for oxidation of cyclooctane showed high performance with a total TON up to 731. The introduction of bulky mesityl groups at β-positions prevented the catalyst deactivation via formation of a μ-oxo dimer.

This study investigates the kinetics and morphology of an equimolar CO2–CH4 gas mixture by inducing sI and sH hydrates in gas–water and gas–liquid hydrocarbon (LHC)–water systems using pure water a...

The commercial dichloro(2-pyridinecarboxylato)gold(III) complex (1), anchored on different carbon materials, is reported for the first time as a catalyst in the cyclohexane hydrocarboxylation to cyclohexanecarboxylic acid. The reaction was carried out in the presence of CO and water, peroxodisulfate, at ca. 50 °C, with 1 in solution and anchored on carbon nanotubes, carbon xerogel or activated carbon, with three different surface chemistries: original forms (CNT, CX or AC, respectively), oxidized with HNO3 (-ox) or oxidized with HNO3 and subsequently treated with NaOH (-ox-Na). 1@CNT-ox-Na was the best catalyst, yielding up to 78% of cyclohexanecarboxylic with a selectivity of 99%. Recycling studies showed that the catalyst was stable up to 4 cycles, the first decrease (11%) on the hydrocarboxylation yield being observed on the 5th cycle. No leaching of gold was found into the solution. The hydrocarboxylation of other cycloalkanes (cyclopentane, cycloheptane and cyclooctane) was also tested in the best conditions found for cyclohexane, but the respective carboxylic acids were obtained in considerably lower yields, which can be explained by different stabilities of cycloalkyl radicals.

A fundamental study on hydrate formation from an equimolar CO2–CH4 gas mixture has been carried out with two focal points: accelerating the kinetics of hydrate formation and enhancing the gas separ...

Seven new modified fusicoccane-type diterpenoids (1-7), together with two known congeners (8 and 9), were obtained from Alternaria brassicicola. Their structures were elucidated from a combination of NMR and HRESIMS data and 13C NMR calculation as well as DP4+ probability analyses, and the absolute configurations of 1-5 were determined by ECD calculation and single-crystal X-ray diffraction (Cu Kα). Compounds 1-3 belong to a rare class of 16-nor-dicyclopenta[a,d]cyclooctane diterpenoids, and compounds 2 and 4 represent the first examples of fusicoccane-type diterpenoids featuring two previously undescribed tetracyclic 5/6/6/5 ring systems, while compound 5 features a previously undescribed tetracyclic 5/8/5/3 ring system. Compound 7 was moderately anti-inflammatory, and compounds 2, 3, 5, and 7 were weakly cytotoxic.

Talaronoids A–D (1–4), four diterpenoids with an unexpected tricyclic 5/8/6 carbon skeleton isolated from Talaromyces stipitatus, represent a new class of fusicoccane diterpenoids and the first examples of natural products with a benzo[a]cyclopenta[d]cyclooctane skeleton. Their structures were established by a combination of extensive spectroscopic analyses and electronic circular dichroism spectral calculations. Plausible biosynthetic pathways of 1–4 are proposed starting from geranylgeranyl diphosphate with a Wagner–Meerwein rearrangement as the key step. Compounds 1–4 were evaluated for butyrylcholinesterase inhibitory activity in vitro, and compounds 1–4 showed moderate activity.

This paper discusses the traditional retouching method of egg tempera, which, amongst other retouching techniques, remains a practised and taught method at the Hamilton Kerr Institute (HKI), University of Cambridge, UK. Since its introduction to Britain, the method has evolved and adapted, most recently owing to the absence of MS2A resin. Laropal A81 has been used as the replacement isolating varnish. However, the physical properties and handling differ from MS2A. The typical diluent used at the HKI for Laropal A81 varnish is a 50:50 mixture of Shellsol A100 and Shellsol D40, however, when used as the isolating resin over an area of retouching this mixture could disrupt lower tempera layers. To remedy this, the diluent was changed to cyclococtane, an aliphatic hydrocarbon. Cyclooctane benefits from being less toxic compared to the aromatic hydrocarbon Shellsol A100 and can be manipulated more on the surface before the activation of lower Laropal A81 layers becomes problematic. Laropal A81 solubilized in cyclooctane was successfully used as the isolating resin for egg tempera retouching and offers promise for a variety of varnishing scenarios and retouching. This paper demonstrates this adapted method of egg tempera retouching through a case study of a 16th-century panel painting with large losses perfectly suited to this method.

The modified second Zagreb index, symmetric difference index, inverse symmetric index, and augmented Zagreb index are among the molecular descriptors which have good correlations with some physicochemical properties (such as formation heat, total surface area, etc.) of chemical compounds. By a random cyclooctane chain, we mean a molecular graph of a saturated hydrocarbon containing at least two rings such that all rings are cyclooctane, every ring is joint with at most two other rings through a single bond, and exactly two rings are joint with one other ring. In this article, our main purpose is to determine the expected values of the aforementioned molecular descriptors of random cyclooctane chains explicitly. We also make comparisons in the form of explicit formulae and numerical tables consisting of the expected values of the considered descriptors of random cyclooctane chains. Moreover, we outline the graphical profiles of these comparisons among the mentioned descriptors.

In this study, we prepared three polymer-anchored Schiff base ligands and their Cu(II), Co(II) and Ni(II) transition metal complexes. For this purpose, we synthesized three Schiff base ligands from the reaction of 2,4-dihydroxybenzaldehyde with diamines in the ethanol solution and characterized by the analytical and spectroscopic methods. We investigated the electrochemical and photophysical properties of the free Schiff base ligands in different solvents and concentrations. In the electrochemical studies, we found that the ligands show the reversible and irreversible redox processes. In order to obtain the polymer-anchored ligands, we used Merrifield’s peptide resin (PS) as solid support. The surface morphologies of the polymer anchored Schiff base ligands were done with the scanning electron microscopy (SEM). We did alkene epoxidation and alkane oxidation reactions of the metal complexes and used the cyclohexene, styrene, cyclohexane and cyclooctane as the substrate and they show the low catalytic activity. The metal complexes have no selectivity in the oxidation reactions. The polymer anchored Schiff base ligands and their metal complexes have high thermal stability at the higher temperatures. Keywords: Schiff base, Solid state, Oxidation, Epoxidation, Thermal

Solvent-tolerant lipase produced by Bacillus sp. DM9K3 has been isolated from the hypersaline area, White Rann of Kachchh, Gujarat, India. The strain initially showed lipase activity of 11.1 U/mL in a basal medium which increased to 52.0 U/mL under optimized culture conditions. Bacillus sp. DM9K3 exhibited stability at 7% salinity, pH 9.0 and 50°C. The extracellular lipase was partially purified by acetone precipitation followed by DEAE-cellulose resulting in 39-fold purification with 40% yield. Metals ions such as Mg2+, Ca2+ and K+ showed enhanced enzyme activity. EDTA did not have a significant effect on activity suggesting that lipase is not metalloenzyme. The lipase under study showed the highest activity when palmitate (C16) was used as a substrate and was also highly stable in organic solvents such as cyclooctane and benzene. The partially purified enzyme was immobilized for increasing the efficiency of the ethyl caprylate (an orange flavored ester) synthesis in the presence of cyclooctane. Additionally, lipase of Bacillus sp. DM9K3 was explored for biodegradation of polycaprolactone microspheres and showed promising results for potential applications in drug delivery system.

This paper reports cyclopentane, cyclohexane and cyclooctane oxidation in the presence of N-hydroxyphthalimide or 4-dodecyloxycarbonyl-N-hydroxyphthalimide in combination with Co(II) and Fe(II) salts using O2/CO2 mixture (0.5 MPa O2, 9.5 MPa CO2). The studies demonstrated that the application of scCO2 in cyclohexane and cyclooctane oxidation processes results in higher conversion and yield of respective ketone and alcohol in comparison to processes performed using air under pressure (0.7 MPa).

A pincer-iridium complex bearing a Lewis-base-free X-type alumanyl ligand has been synthesized. X-ray diffraction, NMR and IR spectroscopy, as well as XANES analysis confirmed its tetrahydrido-IrV structure and Lewis acidity at the Al center as supported by DFT calculations. The resulting complex was applied as a catalyst for the transfer dehydrogenation of cyclooctane.

The reactions of tropospheric oxidants, Cl, OH and O3, with three cyclic hydrocarbons, cyclooctane, cis-cyclooctene and 1,5-cyclooctadiene, have been investigated to understand the significance of these reactions, particularly with Cl, in degradation of these hydrocarbons. The rate coefficients of reaction of Cl (kCl) atom at 298 K are determined as (4.5 ± 0.4), (4.7 ± 0.4) and (5.2 ± 0.7) × 10−10 cm3molecule−1s−1 for cyclooctane, cis-cyclooctene and 1,5-cyclooctadiene. The corresponding values of rate coefficients of reactions with OH (kOH) at 298 K are (1.4 ± 0.2), (5.1 ± 1) and (11.1 ± 2) × 10−11 cm3molecule−1s−1 for cyclooctane, cis-cyclooctene and 1,5-cyclooctadiene, respectively and the values of kO3 at 298 K are (4.1 ± 0.8) and (1.4 ± 0.2) × 10−16 cm3molecule−1s−1 for cis-cyclooctene and 1,5-cyclooctadiene, respectively. The quoted errors include the experimental 2σ, along with the error in the reference rate coefficients. The values of kCl of cis-cyclooctene and kOH of 1,5-cyclooctadiene are being reported for the first time. The results suggest that Cl atom is more effective in the atmospheric degradation of cyclooctane than OH, in the conditions of marine boundary layer. Reactions with both OH and ozone contribute to the degradation of cis-cyclooctene and 1,5-cyclooctadiene, the ozone reaction being more effective in the former and the OH reaction in the latter. Analysis of the stable products suggests that the addition of Cl atom is dominant in the unsaturated molecules. Unsaturated ketones and alcohols are identified as products in the reactions of OH and Cl with cis-cyclooctene and 1,5-cyclooctadiene in the gas phase, emphasizing the importance of H atom abstraction/addition-elimination channels in these unsaturated molecules.

Catalysts for the oxidation of NH3 are critical for the utilization of NH3 as a large-scale energy carrier. Molecular catalysts capable of oxidizing NH3 to N2 are rare. This report describes the use of [Cp*Ru(PtBu2 NPh2 )(15 NH3 )][BArF4 ], (PtBu2 NPh2 =1,5-di(phenylaza)-3,7-di(tert-butylphospha)cyclooctane; ArF =3,5-(CF3 )2 C6 H3 ), to catalytically oxidize NH3 to dinitrogen under ambient conditions. The cleavage of six N-H bonds and the formation of an N≡N bond was achieved by coupling H+ and e- transfers as net hydrogen atom abstraction (HAA) steps using the 2,4,6-tri-tert-butylphenoxyl radical (t Bu3 ArO. ) as the H atom acceptor. Employing an excess of t Bu3 ArO. under 1 atm of NH3 gas at 23 °C resulted in up to ten turnovers. Nitrogen isotopic (15 N) labeling studies provide initial mechanistic information suggesting a monometallic pathway during the N⋅⋅⋅N bond-forming step in the catalytic cycle.

Iridium complexes bearing PCP-type pincer ligands are the most effective catalysts reported to date for the low-temperature (≤ca. 200 °C) dehydrogenation of alkanes. To investigate the activity of formally isoelectronic ruthenium complexes, we have synthesized the neutral 2,7-di-tert-butyl-4,5-bis(diisopropylphosphino)-9,9-dimethylthioxanthene (iPrxanPSP) pincer ligand and several Ru complexes thereof. The (iPrxanPSP)Ru complexes catalyze alkane transfer dehydrogenation of the benchmark cyclooctane/t-butylethylene (COA/TBE) couple with turnover frequencies up to ca. 1 s–1 at 150 °C and 0.2 s–1 at 120 °C, the highest rates for alkane dehydrogenation ever reported at such temperatures. Dehydrogenation of n-octane, however, is much less effective. A combination of experiment and DFT calculations allow us to explain why (iPrxanPSP)Ru is more effective than (iPrPCP)Ir for dehydrogenation of COA, while the reverse is true for dehydrogenation of n-alkanes. Considering only in-cycle species and simple olefin comp...

Aerobic oxidation of hydrocarbons is one of the research fronts in organic chemistry as well as in chemical engineering. In this aspect, many efforts are devoted to develop heterogeneous catalysts that can convert hydrocarbon to its corresponding alcohol/ketone (ol/one) with selectivity more than 90%. However, achieving this target becomes difficult due to possible secondary reactions of initially formed ol/one mixture. Hence, this study aims to report the catalytic activity of Fe(BTC) (BTC: 1,3,5-benzenetricarboxylate) and tetrabutylammonium bromide (TBAB) in aerobic oxidation of cyclooctane at 73% conversion to its respective ol/one with 84% selectivity after 24 h at 120 °C in the absence of any radical initiators. Interestingly, the selectivity of ol/one is higher than 90% at cyclooctane conversion around 20% under present reaction conditions. Reusability and leaching experiments demonstrate the stability of Fe(BTC) during the oxidation reaction. Furthermore, the present catalytic system can also be extended to oxidize other linear hydrocarbons to their respective ol/one products with the selectivity ranging between 88–97 %.

A new Co(II) complex with formula [Co(tptz)Cl2]·2H2O (tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine) has been synthesized and characterized by X-ray crystallography, elemental analyses and spectroscopic methods. It was then supported on modified Fe3O4 nanoparticles using tetraethylorthosilicate (TEOS) and (3-aminopropyl)trimethoxysilane (APTMS) and designated as a Fe3O4@SiO2@APTMS@complex nanocatalyst. The prepared nanocatalyst was characterized by means of FT-IR, Raman, XPS, EDX, XRD, VSM, SEM and TEM studies. The catalytic activity of the [Co(tptz)Cl2]·2H2O complex and Fe3O4@SiO2@APTMS@complex designated as catalysts A and B was used for oxidation of activated secondary alkanes such as fluorene, diphenyl methane, ethylbenzene, cyclooctane and adamantane. Observation of 39–99% conversions and 27–100% selectivities toward the corresponding ketones as well as the heterogeneity and reusability of the catalyst B seem promising.

Mixed-metal metal organic frameworks have received considerable attention in recent years and it has been shown that the activity of the parent metal organic framework (MOF) is often enhanced upon doping with external metal ions within the framework. In this context, Cu2+ ions with different loadings were incorporated within the ZIF-8 framework to obtain a series of Cu-doped ZIF-8 materials and their activity was examined in the aerobic oxidation of hydrocarbons. The as-synthesized Cu-doped solids were characterized by powder X-ray diffraction (XRD), ultraviolet diffuse reflectance spectroscopy (UV-DRS), scanning electron microscopy (SEM), Fourier Transform infrared (FT-IR), electron paramagnetic resonance (EPR) and inductively coupled plasma (ICP) analysis. The experimental results revealed that the activity of Cu-doped ZIF-8 is much higher than that of the parent ZIF-8 in all the tested substrates at 120 °C. Furthermore, the activity of the Cu-doped ZIF-8 with the highest Cu loading was eight fold higher than that of the parent ZIF-8 in the aerobic oxidation of cyclooctane (1) at 120 °C with more than 80% selectivity to the corresponding cyclooctanol/cyclooctanone (ol/one) mixture. Cu-doped ZIF-8 was reused two times with no significant drop in its activity under identical conditions. Furthermore, comparison of the two times reused solid with that of the fresh solid by powder XRD and SEM analysis revealed identical structural integrity and morphology, respectively during the oxidation reactions.

The surface properties of two sepiolite samples and one palygorskite sample were compared using inverse gas chromatography (IGC). Samples were previously conditioned at appropriate temperatures for the removal of all zeolitic water. Dispersive (or Lifshitz–van der Waals) component of the surface energy (γsd), specific interactions (−ΔGas) with π electron donor bases (1-alkenes), and nanomorphology indices (IMχT) based on the injections of cycloalkanes and a branched alkane were measured. From IGC data, at 240 °C, it was found that the palygorskite was clearly distinguished from the sepiolites. The palygorskite possessed a lower γsd, larger −ΔGas with 1-alkenes, and remarkably higher IMχT. Slight differences could also be observed between the two sepiolite samples with the same origin. The results were rationalized in terms of the structural features of the two studied minerals. The larger channels of the sepiolite allow for a better insertion of the n-alkanes (longer retention times) while excluding the bulkier probes, such as cyclooctane or 2,2,4-trimethylpentane. Accordingly, the corresponding γsd values were larger and the IMχT values were lower (higher surface nanoroughness) for the sepiolites. Regarding Lewis acid–base properties, all the sample’s surfaces evidenced a very strong amphoteric character. The present results highlight the potential of the evaluated samples for, e.g., adsorption processes with volatile organic compounds or matrix–filler interactions regarding the production of composite structures with Lewis acid–base matrices.

International audience; Using a synthetic method, the phase behavior of the CO2 (1) + cyclooctane (2) binary system was for the first time experimentally studied between 292.95 K and 373.55 K. In this temperature range, the bubble- and dew-point pressures, ranging from 13.2 to 183.4 bar were measured for carbon dioxide mole fractions between 0.1014 and 0.9701. A total of 96 experimental data points were acquired. The experimental data were obtained using a high-pressure cell by visual observation of phase transitions. These measurements made it possible to conclude that the studied binary system probably exhibits a type V phase behavior in the classification scheme of Van Konynenburg and Scott. In particular, the experimental temperature of the suspected lower critical end point (LCEP) was found to be 303 K. Despite the complexity of the phase behavior, the experimental data could be accurately correlated with the Peng-Robinson equation of state combined with sophisticated mixing rules that either involve temperature-dependent binary interaction parameters (kij(T)) or that embed the residual part of the Wilson activity coefficient model.

The efficient synthesis of two new stereoisomeric 3-aminocyclooctanetriols and new halocyclitol derivatives of them starting from cis,cis-1,3-cyclooctadiene are reported. Reduction of cyclooctene endoperoxide, obtained by photooxygenation of cis,cis-1,3-cyclooctadiene, with zinc yielded a cyclooctene diol followed by acetylation of the hydroxyl group, which gave dioldiacetate by OsO4/NMO oxidation. The cyclooctane dioldiacetate prepared was converted to the corresponding cyclic sulphate via the formation of a cyclic sulphite in the presence of catalytic RuO4. Reaction of this cyclic sulphate with a nucleophilic azide followed by the reduction of the azide group provided the target, 3-aminocyclooctanetriol. The second key compound, bromotriol, was prepared by epoxidation of the cyclooctene diol with m-chloroperbenzoic acid followed by hydrolysis with HBr(g) in methanol. Treatment of bromotriol with NaN3 and the reduction of the azide group yielded the other 3-aminocyclooctanetriol desired. Hydrolysis of the epoxides with HCl(g) in methanol gave stereospecifically new chlorocyclooctanetriols.

The conformational properties of ring compounds such as cycloalkanes determine to a large extent their stability and reactivity. Therefore, the investigation of conformational processes such as ring inversion and/or ring pseudorotation has attracted a lot of attention over the past decades. An in-depth conformational analysis of ring compounds requires mapping the relevant parts of the conformational energy surface at stationary and also at non-stationary points. However, the latter is not feasible by a description of the ring with Cartesian or internal coordinates. We provide in this work, a solution to this problem by introducing a new coordinate system based on the Cremer–Pople puckering and deformation coordinates. Furthermore, analytic first- and second-order derivatives of puckering and deformation coordinates, i.e., B-matrices and D-tensors, were developed simplifying geometry optimization and frequency calculations. The new coordinate system is applied to map the potential energy surfaces and reaction paths of cycloheptane (C7H14), cyclooctane (C8H16), and cyclo[18]carbon (C18) at the quantum chemical level and to determine for the first time all stationary points of these ring compounds in a systematic way.

Abstract Crystalline hybrid catalysts based on molybdenum or tungsten oxide and aliphatic diamines were synthesized via simple, eco-friendly reproducible methodologies, starting from commercially available and relatively inexpensive organic and inorganic precursors, and using water as solvent under mild conditions. The crystal structures of the obtained fine powdered solids were solved ab initio from powder X-ray diffraction data. The type of organic component (1,2-diaminoethane, 1,2-diaminopropane, 1,3-diaminopropane) may play a structure-directing role. On the other hand, different metals (M = Mo, W) may lead to isostructural one-dimensional hybrids of the type MO3(L) with the same bidentate diamine ligand L. The prepared catalysts were investigated for the liquid phase oxidation of saturated and unsaturated hydrocarbons (cis-cyclooctene, cyclooctane), using different types of oxidants (O2, H2O2, tert-butyl hydroperoxide). Differences in catalytic performances associated with distinct structural features were investigated. Graphic Abstract

Undoubtedly, cyclooctane has been investigated theoretically and experimentally, however, considering the vast application of cycloalkanes and limited research for the higher members, the reactivity and structural investigation of cyclooctane, fluorocyclooctane, bromocyclooctane, chlorocyclooctane, azocane, oxocane and thiocane have been explored using density functional theory (DFT) method. In this work, we reported elaborately on some molecular and electronic properties. Interestingly, the condensed dual descriptors ( Δ f ); Br24 of bromocyclooctane compound and N22 of azocane compound has the highest positive values of 0.3561eV and 0.1618eV respectively and hence, potential sites for nucleophilic reaction compared to chlorocyclooctane, fluorocyclooctane, oxocane, thiocane and the parent cyclooctane. In the UV-VIS spectroscopic analysis, σ-π* nor π to π* transitions where observed for all the studied molecules and these molecules are expected to be colorless due to the absence of an absorption band in the visible region (380–760 nm). In all the substituted cyclooctane molecules investigated, C–F bond of fluorocyclooctane is more polar than C–O, C–S, C–N, C–Cl, C–Br bonds of other compounds. The interactions between the lone pair (LP (1) N22) and antibonding; σ*(1)C4–C5 of azocane gave the highest stabilization energy (10.44 kcal/mol) compared to other compounds investigated. We believe our detail reported work on this eight-membered ring compound and its derivatives will widen the scope of these molecules to other researchers.

A synthetic method to prepare bicyclo[6.3.0]undeca-2,4,9,trienyl esters efficiently from gold(I)-catalyzed Rautenstrauch rearrangement/1,5-hydride shift/8-endo-dig cyclization of 1-ene-4,10-diynyl esters is described. The suggested double cycloisomerization mechanism delineates the first example of an unactivated all-carbon tethered 1,7-enyne, either preformed or formed in situ, which undergoes an 8-endo-dig cyclization pathway to give a cyclooctane motif. It also offers an extremely rare synthetic method in organic chemistry that can sequentially assemble both ring components of the bicyclic motif from an acyclic precursor in one step.

Autoxidation of cycloalkanes (C5–C8) with molecular oxygen under catalyst-free and solvent-free conditions was conducted systematically for the first time, focusing on the autoxidation temperature and product distribution. The autoxidation of cyclopentane, cyclohexane, cycloheptane and cyclooctane occurs at 120 °C, 130 °C, 120 °C, and 105 °C respectively, with obvious oxidized products formation. At 140 °C, 145 °C, 130 °C and 125 °C, acceptable yields of the oxidized products could be obtained for them, and the oxidized product distributions were investigated in detail. The autoxidation of cycloalkanes follows the pseudo-first-order kinetic model and the apparent activation energies (Ea) for the autoxidation of cyclopentane and cyclohexane are 159.76 kJ·mol− 1 and 86.75 kJ·mol− 1 respectively. This study can act as an important reference in screen of suitable reaction temperature and comparison of the performance of various catalysts in the catalytic oxidation of cycloalkanes in the attempt to enhance the oxidized product selectivity.

A series of tBu- and iPr-substituted PNP–pincer Ir and Rh complexes with pyrrole-based core were synthesized and characterized. The structures of the obtained complexes were varied depending on the size of alkyl substituents and ligands other than PNP ligand. All of them exhibit low activity toward transfer dehydrogenation of cyclooctane., ファイル公開：2019-04-23

A series of polycyclic hydrocarbons containing cyclopropane moieties 1,2-annelated or spiro-condensed with cyclooctane ring were investigated under oxidative conditions. Four oxidizing systems (O3 on SiO2, dioxirane derived from trifluoroacetone, CrO3 and RuO4, generated in situ), were employed to evaluate and compare their reactivity and usefulness. RuO4 was found to be the best one, considering its oxidative power together with a simple preparative procedure. The conditions for specific oxidation of polycyclic hydrocarbons were found. Novel cyclooctane derivatives containing cyclopropyl carbonyl moieties were obtained.

Syntheses of new asymmetric pincer precursors 1,3-C6H4{CH2P(tBu,X)}2 (tBu,XPCPH; X = Cl, SiMe3, OPh) and a new class of hybrid donor/acceptor pincer ligands 1,3-C6H4{CH2P(tBu,Rf)}2 (tBu,RfPCPH; Rf = CF3, C2F5) are reported. All tBu,XPCPH compounds are obtained as mixtures of meso and rac diastereomers in varying ratios (meso : rac ∼ 4 : 1 to 3 : 2) which were used without separation. Treatment of Ru(cot)(cod) with tBu,CF3PCPH under 1 atm H2 in acetone at 20 °C produced the hydride solvate (tBu,CF3PCP)Ru(acetone)xH which was not isolated, but could be trapped as stable diene complexes (tBu,CF3PCP)Ru(L)2H (L2 = cod (), nbd ()). Catalytic cyclooctane dehydrogenation studies demonstrate that has ∼50% the activity of (CF3PCP)Ru(cod)(H), but significantly higher catalyst stability and is able to operate at higher catalyst loading concentrations without deactivation via bimolecular decomposition.

Altering the cultivation conditions, such as temperature, media compositions, illumination, aeration, the shape of the culturing flask, etc., is regarded as a useful strategy for the exploitation of structurally novel and bioactive secondary metabolites, which inspired us to explore the chemical and pharmacological diversities from the genetically powerful fungus Alternaria brassicicola. As a result, twelve fusicoccane-type diterpenoids, including eight new ones, termed brassicicenes Q-X (1-8), were isolated from a modified rice medium. Biosynthetically, all these compounds were derived from the mevalonic acid (MVA) pathway, and their structures incorporating absolute configurations were assigned by the interpretation of spectroscopic (HRESIMS and 1D and 2D NMR) analyses, chemical conversion, a modified Mosher's method, 13C NMR calculation, and single-crystal X-ray diffraction (Cu Kα). Structurally, compound 1 was an unusual 16-nor-dicyclopenta[a,d]cyclooctane diterpenoid bearing a fused cyclopent-2-en-1-one moiety. In addition, compound 3 was found to show significant anti-inflammatory activity against the production of NO, TNF-α, and IL-1β at 10 μM. Further western blot and immunofluorescence experiments found the mechanism of action to be that 3 inhibited the NF-κB-activated pathway, highlighting it as a promising starting point for the development of new anti-inflammatory agents.

Despite the difficulty in administering a safe dose regimen and reports of emerging resistance, warfarin (1) remains the most widely-used oral anticoagulant for the prevention and treatment of thrombosis in humans globally. Systematic substitution of the warfarin phenyl ring with either 1,3,5,7-cyclooctatetraene (COT) (2), cubane (3), cyclohexane (4) or cyclooctane (5) and subsequent evaluation against the target enzyme, vitamin K epoxide reductase (VKOR), facilitated interrogation of both steric and electronic properties of the phenyl pharmacophore. The tolerance of VKOR to further functional group modification (carboxylate 14, PTAD adduct 15) was also investigated. The results demonstrate the importance of both annulene conferred π-interactions and ring size in the activity of warfarin.