Cyclic Alcohols Research Articles

Interfacial catalytic influence of sodium lauryl sulphate in the oxidation of cyclic alcohols by Cr(VI)

In the present work effort has been made to investigate the electron transfer mechanism for the oxidation of cyclopentanol of importance be Cr(VI) in presence and absence of surfactant (Sodium lauryl sulphate, SDS) and develop a kinetic model. The progress of the reaction was monitored spectrophotometrically by measuring the fall in absorbance of Cr(VI) at its λmax (wave-length of maximum absorbance). Under the conditions of [cyclopentanol] >≫ [Cr(VI)], the ln(Absorbance) vs time plots are obtained having constant slope value indicating the reaction exhibited a first order dependence with respect to Cr(VI). Unit order dependence of rate on [cyclopentanol], complex dependence on acid strength, nil effect of added salt (K2SO4) is what we observed while monitoring the progress of the reaction. The thermodynamic parameters like activation energy, enthalpy, entropy is computed by executing the reaction at 25, 30 and 35 0C. In presence of varying [SDS] it is observed that the rate marginally increases with increase in [SDS] until an optimum [SDS] which is around cmc and there after the rate decreases exponentially. In SDS medium partitioning of both the cationic Cr(IV) species and the substrate between water and micellar pseudo-phase is considered and accordingly Berezin et al. model is extended to explain the kinetic data. Based on all experimental findings a suitable kinetic model has been proposed for both aqueous and micellar phase reaction.

Remote Electronic Tuning of Chiral N-Heterocyclic Carbenes.

Our recent efforts to develop novel N-Heterocyclic carbene (NHC)-catalyzed asymmetric reactions are described. During our investigation for development of the acylation reactions via acylazoliums generated by the reactions of NHCs and α-oxidized aldehydes, we have observed significant effects of substitution at a remote site of the carbene carbon of NHCs. In addition, we also observed a significant enhancement of the enantioselectivity by the addition of carboxylate anions. From this observation, we proposed a novel working hypothesis involving a formation of a complex of the substrate and additive to reinforce the recognition of the catalyst for enhancement of the catalytic performance of the asymmetric N-heterocyclic carbene system. By applying this concept, we achieved the kinetic resolutions of both cyclic and acyclic alcohols in excellent enantioselectivities. The effects of the remote substitution were also observed in intramolecular Stetter reaction and intermolecular benzoin reaction. In these reactions, the comparison of the catalytic performance of the NHCs bearing variable remote substitutions provided insights into the reaction mechanism because the remote substitution tuned the electronic nature of NHCs without affecting the steric and electrostatic factors around the reaction site. We also developed an intramolecular benzoin condensation involving two aldehydes, which is challenging to realize. Using the substrates bearing proper protecting groups, we succeeded in the stereo divergent synthesis of a variety of inososes, which are important intermediates for the synthesis of biologically active cyclitols.

Facile synthetic route of TiO2–ZnO heteronanostructure coated by oxovanadium (IV) bis-Schiff base complex as a potential effective homogeneous/heterogeneous catalysts for alcohols redox systems

Oxovanadium (IV) bis-Schiff base complex was synthesized by a facile complexation of 2 molar ratio of 2‑hydroxy-Schiff base ligand (HL) with 1 molar ratio of VO2+ ion giving mononuclear VOL2 complex with a square pyramidal geometry. The structure conformation of HL and its corresponding VOL2 complex was assigned within various spectroscopic tools (IR, UV–vis. Mass spectra), as well as the elemental analyses (EA). The deprotonated 4-OH group in VOL2 caused a successful coating of VOL2 on a mixed oxides of TiO2–ZnO nanoparticles awarding nanocomposite of TiO2–ZnO@VOL2. By applying alternative analytical techniques, the surface morphology and internal structure TiO2–ZnO@VOL2 nanocomposites were investigated compared to that of TiO2–ZnO, i.e. by XRD, FESEM, HR-TEM, EDS and IR spectra), and also with TGA and BET (adsorption–desorption isotherm).The catalytic effectiveness of both homogeneous and heterogeneous catalysts (VOL2 and TiO2–ZnO@VOL2) was examined in the productive oxygenation reactions of BA (benzyl alcohol) by an aqueous hydrogen peroxide under an aerobic environment to the chemo-selective product benzaldehyde (BZ), and benzoic acid (BO), as the overodixation product. Both VOL2 and TiO2-ZnO@VOL2 catalysts exhibited obvious classified action by 89% and 91% yielding amount of benzaldehyde after 4 h for reaction temperature 80 and 90 °C, respectively. The differentiation between them in the catalytic reactivity was depending on the heterogeneity and the effect of the coated TiO2–ZnO nanoparticles on the VOL2 catalytic potential. The kinetic parameter of the productive redox protocols for both catalyst was examined. Additionally, some other cyclic and acyclic alcohols were exhibited the productive redox protocol in the optimum control of both catalysts.

Analysis of thermodynamics, kinetics, and reaction pathways in the amination of secondary alcohols over Ru/SiO2

This work considers the Ru-mediated amination of secondary alcohols with ammonia in vapor and liquid media. We map thermodynamic constraints, and we probe the impacts of species partial pressure, residence time, and reaction temperature on rate, selectivity, and catalyst stability. Alcohol amination consumes no H2, and H2 has no significant impact on amination kinetics; however, operating under H2 benefits Ru stability. Primary amine selectivity increases with ammonia pressure and alcohol conversion, and the latter observation is consistent with the formation of primary amines through a network of sequential reactions. Unfortunately, primary amines are susceptible to secondary deamination to form hydrocarbons. As is typical of processes that seek to isolate a reactive intermediate, the main selectivity challenge here is identifying residence times that are long enough to accumulate high substrate conversion but short enough to avoid secondary deamination. In general, moderate residence times will maximize the production of primary amines. Insights extend across a broad substrate scope, and we observe 70 – 90% yield of primary amines from linear, cyclic, and heterocyclic alcohols. That said, heterocyclic alcohols appear susceptible to product inhibition, so achieving high conversions requires longer residence times and/or increased ammonia pressures.

Photocatalytic annulative cyanoalkyletherification of 1,6-enynes toward 1-indanones

A concise and operationally simple photocatalysis strategy for the annulative cyanoalkyletherification of 1,6-enynes with cyclic oxime esters and alcohols is reported, producing a set of functionalized 1-indanones bearing an all-carbon quaternary center with generally good yields. In this process, single electron reduction of cyclic oxime esters drives deconstructive carbon−carbon σ-bond cleavage to yield a key cyanopropyl radical poised for addition−cyclization. This reaction is redox-neutral and demonstrates good functional group compatibility and a wide substrate scope, in which diversified alcohols can be engaged in the annulation reaction to prepare exocyclic vinyl ethers.

Deconstructive Cyanomethylation Enabled by Radical Cross‐Coupling through Multiple C−C Bond and C−H Bond Cleavage

AbstractBeing in its infancy, radical cross‐coupling is highly efficient for C−C bond construction, though suffers from selectivity problems and limited reaction types. New methodologies to realize radical cross‐coupling selectively are highly desired. Herein, an iron catalyzed deconstructive cyanomethylation of unstrained cyclic and linear alcohols with acetonitrile has been developed through radical cross‐coupling. The unprecedented method enables a ring‐opening functionalization of cyclohexanols to produce α‐cyanomethyl ketones. Notably, the highly challenging reaction involves twice C−C single bond cleavage through β‐scission of alkoxyl radical intermediates, and twice C(sp3)−H bond transformation via hydrogen atom transfer (HAT) procedures, resulting in two carbon radical species that realize a radical cross‐coupling process to form a new C(sp3)−C(sp3) bond selectively. α‐arylketo and α‐aryl substituted tertiary alcohols can also be applied as substrates, leading to terminal cyano‐functionalized linear products, with ketone as the leaving fragment. Mechanistically, a new procedure to generate alkoxyl radical with chlorine radical through the in‐situ formed intermediate cycloalkyl hypochlorite was suggested.magnified image

Martin Silicates as Partners in Photoredox/Ni Dual Catalysis for the Installation of CH3, CH2D, CD2H, CD3and13CH3Groups onto (Hetero)Arenes

Martin Silicates as Partners in Photoredox/Ni Dual Catalysis for the Installation of CH₃, CH₂D, CD₂H, CD₃and¹³CH₃Groups onto (Hetero)Arenes

Stereoselective Synthesis of Novel (±)-trans-Dihydronarciclasine Analogues: Preparation of a Pivotal Intermediate Containing Two Methoxy Substituents

An efficient stereoselective synthesis of a pivotal intermediate, a cyclic allyl alcohol derivative containing two methoxy groups [(±)-22], using for the preparation of (±)-trans-dihydronarciclasine analogues was elaborated starting from easily available and inexpensive methyl gallate. This new synthetic route consists of 17 reaction steps, and provides an opportunity to obtain the wanted alkaloid derivative containing an additional methoxy group at position 11, in the ring A of the phenanthridone scaffold.

Nickel-Catalyzed α-Alkylation of Arylacetonitriles with Challenging Secondary Alcohols.

Nickel(II) complex 1 was utilized as a sustainable catalyst for α-alkylation of arylacetonitriles with challenging secondary alcohols. Arylacetonitriles with a wide range of functional groups were tolerated, and various cyclic and acyclic secondary alcohols were utilized to yield a large number of α-alkylated products. The plausible mechanism involves the base-promoted activation of precatalyst 1 to an active catalyst 2 (dehydrochlorinated product) which activates the O-H and C-H bonds of the secondary alcohol in a dehydrogenative pathway.

Multi-structural variational kinetics study on hydrogen abstraction reactions of cyclopentanol and cyclopentane by hydroperoxyl radical with anharmonicity, recrossing and tunneling effects.

To date, it is still a challenge to accurately predict the reaction kinetics of H-atom abstractions by the HO2 radical in cycloalkanes and cyclic alcohols, which plays a fundamental role in both atmospheric and combustion chemistry. Cyclopentanol (CPL) is a novel alternative fuel derived from lignocellulosic biomass, while cyclopentane (CPT) is a representative component in conventional fossil fuels. Both are promising gasoline additives due to their high-octane and knock-resistant features, and therefore selected as our target molecules for detailed theoretical investigation in this work. The rate constants of H-abstraction by HO2 over a wide temperature range of 200-2000 K were calculated using multi-structural variational transition state theory (MS-CVT) in multi-dimensional small-curvature tunneling approximation (SCT) including multiple structural and torsional potential anharmonicity (MS-T), recrossing and tunneling effects. For comparison, the "single-structural rigid-rotor quasiharmonic oscillator" (SS-QH) rate constants corrected by multi-structural local harmonic approximation (MS-LH) and different quantum tunneling methods including one-dimensional Eckart and zero-curvature tunneling (ZCT) were also obtained in this work. The importance of considering the anharmonicity, recrossing and multi-dimensional tunneling effects was stressed by analyzing the MS-T and MS-LH factors and transmission coefficients for each studied reaction. In general, the MS-T anharmonicity was found to increase the rate constants by certain values especially at high temperatures; the multi-dimensional tunneling effect significantly increased the rate constants at low temperatures as expected; and the recrossing effect decreased the rate constants but it was only remarkable for the α and β carbon sites in CPL and the secondary carbon site in CPT. The comparison of the results from the different theoretical kinetic corrections in this work or empirically estimated methods from the literature showed significant deviations in the site-specific rate constants, branching ratios (competition of different channels) and Arrhenius activation energies with pronounced temperature dependence.

Получение и исследование свойств сульфосукцинатов циклических спиртов для применения в технологии хранения и транспортировки газа в гидратной форме

The article presents the synthesis of several cyclic alcohol sulfosuccinates and the study results of their influence on the kineticsof methane hydrate formation in high-pressure autoclaves. The effect of the structure of the tested compounds on foaming, induction time, and water-to-hydrate conversion is considered in comparison with sodium dodecyl sulfate. The process of obtaining the substances used is presented in detail. It was found that an increase in the size of the cycloalkyl fragment from C5 to C7 leads to some acceleration of the nucleation and growth of methane hydrate. In contrast, the transition to a cycle containing eight carbon atoms decreasesthe promoting effect. It is shown that the impact of the synthesized compounds on accelerating the formation of gas hydratesis comparable to that for sodium dodecyl sulfate. At the same time, the proposed reagents possess better performance characteristics (do not contribute to foaming).

Ru complexes containingN‐methyl‐1,3,5‐triaza‐7‐phosphaadamantane (mPTA) as catalysts for the isomerization of 2‐cyclohexen‐1‐ol

The complex [RuCp(H2O‐κO)(mPTA)2](CF3SO3)3·MeOH (4·MeOH) was synthesized and characterized by spectroscopic techniques and its crystal structure determined by single‐crystal X‐ray diffraction (mPTA = N‐methyl‐1,3,5‐triaza‐7‐phosphaadamantane). The catalytic activity of4for the redox isomerization of 2‐cyclohexen‐1‐ol into cyclohexanone was studied in water, methanol/water, and biphasic systems, reaching the highest conversion rate in biphasic water/cyclohexane (1:1) at pH 1.7 and under N2. The aqueous phase containing4was recycled up to 7 consecutive runs, reaching a total turnover number (TON) of 471 without significant losses of catalyst. Therefore, this reaction is a unique procedure for the isomerization of cyclic allylic alcohols without metal contamination of the product. The catalytic reaction mechanism was studied by nuclear magnetic resonance (NMR), showing that the reaction probably proceeds through the formation of an intermediate in which the substrate is η2‐coordinated to the metal.

Nickel-Catalyzed Direct Synthesis of N-Substituted Indoles from Amino Alcohols and Alcohols.

A one-pot cascade approach for the synthesis of N-substituted indoles from amino alcohols and alcohols under additive and base-free conditions with the liberation of water as the only stoichiometric byproduct is reported. The commercially available bench-stable Ni(OTf)2 salt in combination with 1,2-bis(dicyclohexylphosphino)ethane (dcype) is very effective for this unprecedented catalytic transformation. A broad range of substrates including aromatic and aliphatic primary alcohols, cyclic and acyclic secondary alcohols, and various substituted 2-aminophenyl ethyl alcohols are employed in the reaction conditions to provide a diverse range of N-alkylated indoles. Mechanistic studies revealed that the reaction proceeds through tandem N-alkylation via hydrogen autotransfer followed by the cyclization of N-alkylated alcohol intermediate.

A Neutral FeCl3 Photocatalysis for C–C Bond Animation and Alkylation of Cyclic Alcohols

AbstractA modified method for iron-catalyzed C–C bond cleavage and amination and alkylation of nonactivated cyclic alcohols has been developed. Using FeCl3 as catalyst, the photoinduced ligand-to-metal charge transfer facilitates the generation of O-radicals from alcohols, the subsequent β-scission, and finally the radical trapping. Compared with the Fe(OR)3 catalysis, this mildly base-free system could enable the amination in a broader substrate scope with higher yields. Moreover, the C–C bond cleavage and alkylation of cyclic alcohols proceeds with electron-deficient olefins under these conditions.

Structure identification of binary (cyclic alcohol guests + methane) clathrate hydrates using Rietveld analysis with the direct space method

Herein, the alcohol inclusion and interactions occurring in binary (cyclobutanol + CH4), (cyclopentanol + CH4), and (cyclohexanol + CH4) clathrate hydrates were investigated using Rietveld analysis with the direct space method. The alcohol geometry in the hydrate cages of the binary-hydrates was examined using 13C solid–state nuclear magnetic resonance spectroscopy and density function theory calculations. Structural characterization of the binary-hydrates indicated that OH groups of the alcohols may interact with the host-framework via hydrogen-bonding. Additionally, the possibility of OH group incorporation of cyclic alcohols into the host framework should be conducted in the future.

Menthol nanoliposomes enhanced anti-tumor immunotherapy by increasing lymph node homing of dendritic cell vaccines

Menthol, a cyclic terpene alcohol, plays a critical role in overcoming the blood-brain barrier and stratum corneum barrier. Herein, we innovatively propose a menthol nanoliposome (Men-nanoLips) that can dramatically increase lymph node accumulation of the dendritic cell (DC)-based anti-tumor vaccines. Specifically, Men-nanoLips efficiently enhanced lymphatic endothelial cell (EC) barrier permeability by reducing the expression of tight junction proteins. And interestingly, Men-nanoLips not only up-regulated the expression of CCR7 in DCs but also increased the secretion of CCL21 in lymphatic ECs. Moreover, Men-nanoLips promoted DC vaccine maturation as evidenced by increasing the expression of costimulatory molecules and up-regulating the pseudopodia-like protein. With those complementary mechanisms provided by Men-nanoLips, the number of the B16 whole-tumor cell lysate-loaded DCs that target the draining LN enhanced remarkably and significantly boosted the treatment efficacy of DC anti-tumor vaccines. Therefore, we concluded that Men-nanoLips could be instructive for increasing LN homing of DC vaccines.

Physiological, Biochemical, and Structural Bioinformatic Analysis of the Multiple Inositol Dehydrogenases from Corynebacterium glutamicum.

ABSTRACTInositols (cyclohexanehexols) comprise nine isomeric cyclic sugar alcohols, several of which occur in all domains of life with various functions. Many bacteria can utilize inositols as carbon and energy sources via a specific pathway involving inositol dehydrogenases (IDHs) as the first step of catabolism. The microbial cell factory Corynebacterium glutamicum can grow with myo-inositol as a sole carbon source. Interestingly, this species encodes seven potential IDHs, raising the question of the reason for this multiplicity. We therefore investigated the seven IDHs to determine their function, activity, and selectivity toward the biologically most important isomers myo-, scyllo-, and d-chiro-inositol. We created an ΔIDH strain lacking all seven IDH genes, which could not grow on the three inositols. scyllo- and d-chiro-inositol were identified as novel growth substrates of C. glutamicum. Complementation experiments showed that only four of the seven IDHs (IolG, OxiB, OxiD, and OxiE) enabled growth of the ΔIDH strain on two of the three inositols. The kinetics of the four purified enzymes agreed with the complementation results. IolG and OxiD are NAD+-dependent IDHs accepting myo- and d-chiro-inositol but not scyllo-inositol. OxiB is an NAD+-dependent myo-IDH with a weak activity also for scyllo-inositol but not for d-chiro-inositol. OxiE on the other hand is an NAD+-dependent scyllo-IDH showing also good activity for myo-inositol and a very weak activity for d-chiro-inositol. Structural models, molecular docking experiments, and sequence alignments enabled the identification of the substrate binding sites of the active IDHs and of residues allowing predictions on the substrate specificity.IMPORTANCE myo-, scyllo-, and d-chiro-inositol are C6 cyclic sugar alcohols with various biological functions, which also serve as carbon sources for microbes. Inositol catabolism starts with an oxidation to keto-inositols catalyzed by inositol dehydrogenases (IDHs). The soil bacterium C. glutamicum encodes seven potential IDHs. Using a combination of microbiological, biochemical, and modeling approaches, we analyzed the function of these enzymes and identified four IDHs involved in the catabolism of inositols. They possess distinct substrate preferences for the three isomers, and modeling and sequence alignments allowed the identification of residues important for substrate specificity. Our results expand the knowledge of bacterial inositol metabolism and provide an important basis for the rational development of producer strains for these valuable inositols, which show pharmacological activities against, e.g., Alzheimer’s disease, polycystic ovarian syndrome, or type II diabetes.

Cobalt-catalyzed O-arylation of N-protected amino alcohols with arenes via cross-dehydrogenative C-O coupling strategy: Direct access to aryloxyamines

An efficient Co(II)-catalyzed cross-dehydrogenative C-O coupling strategy for the arylation of N-protected amino alcohols, including 1,2-, 1,3- and 1,4-amino alcohols, branched amino alcohols and cyclic amino alcohols with different amides derivatives has been developed, affording a wide range of corresponding aryloxyamines compounds with excellent convertibility in moderate to good yields, which are of great interest in medicinal and pharmaceutical chemistry. Furthermore, this reaction system could be further applied to the preparation of potential bioactive molecules.

Diastereo- and regioselective petasis aryl and allyl boration of ninhydrins towards synthesis of functionalized indene-diones and dihydrobenzoindeno-oxazin-ones.

Petasis aryl and allyl borations were accomplished using substituted ninhydrins, boronic acids or 2-allyl-4,4,5,5-tetramethyl-1,3,2-dioxaborolane and 1,2-aminophenols in Hexafluoroisopropanol (HFIP) without any catalysts to synthesize different aryl and allyl derivatives of ninhydrins. The nature of substitution in the boronic acids and 1,2-amino phenols was the key factor in determining the diastereo-regioselectivity and the type of product distributions. The products were isolated and characterized by HMBC, HSQC, 1H, 13C NMR experiments and X-ray single crystallographic analysis. A probable reaction pathway involves in situ formation of acyclic and cyclic ninhydrin-amino alcohol adducts, with the positioned hydroxyl group determining the stereo-regioselective outcome via tetracoordinated boron intermediates. A metal free diastereo- and regioselective Petasis aryl and allyl boration of ninhydrins.

Access to Hexahydroindeno[2,1-c]pyran-Based Propellanes by a Domino Prins/Friedel–Crafts Cyclization

AbstractStarting from readily available cyclic homoallylic alcohols, a Prins reaction allowed the formation of a bicyclic tetrahydropyranyl carbocation intermediate that is only trapped by electron-rich aromatic rings according a further intramolecular Friedel–Crafts reaction leading to new [4.4.3]propellane structures.