Cyclic Alcohols Research Articles

An improved synthesis of alkyl AMP esters

Enzymes belonging to the Acyl-CoA/NRPS/Luciferase (ANL) superfamily of enzymes, are significant targets in drug development. One member of this superfamily is Acetyl-CoA Synthetase (ACS). This enzyme is an emerging target for the treatment of various infectious diseases and cancer. Alkyl AMP esters have emerged as potent inhibitors of ACS. Previous methods for synthesizing these esters often involved water-based reactions or necessitate purification through reverse phase prep-HPLC or ion-exchange chromatography. To address these challenges, we developed a new approach utilizing 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) to couple 5′-adenylic acid to the corresponding alcohol, utilizing triethylamine as the base. This method yielded primary, secondary, unsaturated, and cyclic alcohols in excellent yields. Importantly, we optimized the reaction conditions to achieve excellent yield and purity without the need for reverse phase prep-HPLC or ion exchange chromatography. Instead, purification was achieved through silica gel chromatography using Biotage ® Sfar spherical silica gel.

Nature of host–guest interaction of cyclic alcohols in β-Cyclodextrin: A molecular view of its structural features

Host- guest complexes are commonly found in several disciplines such as biochemistry, cosmetics, food, pharmaceuticals, and the environment. Studying the relationships between host and guest is essential in this context to understand their physicochemical behavior. This study aimed to examine the intermolecular interactions of cyclic alcohols within β-cyclodextrin (β-CD). The experimental spectroscopic results demonstrated the formation of the studied complexes. In this work, two orientations were used: orientation A (hydroxyl group toward the primary hydroxyl of β-CD) and orientation B (hydroxyl group toward the secondary hydroxyl of β-CD). The results indicate that regardless of the orientation used, the profile energy is thermodynamically favorable. However, there are differences in terms of greater or less stability in terms of the thermodynamic parameters studied. Physicochemical properties demonstrate that the host–guest complex forms spontaneously, and exothermic mode. The interaction between cyclic alcohols and β-CD in orientation A promotes a more pronounced deformation of the secondary edge of β-CD. Moreover, the arrangement of moleculesdemonstrates that intramolecular hydrogen bonds are less stable between the glycosidic units of β-CD. This arrangement may help or hinder the development of intermolecular hydrogen bonds.

Modeling the thermodynamic properties of cyclic alcohols with the SAFT-γ Mie approach: application to cyclohexanol and menthol systems

Cyclic alcohols are commonly found in natural and synthetic products and are involved in many biological processes. An ability to model their thermodynamic properties is of interest in food, flavouring, and pharmaceutical manufacturing, particularly for mixtures for which available experimental data are limited. Good examples are mixtures including menthol, a naturally occurring cyclic alcohol widely used in the food and pharmaceutical industries, well-known for its cooling-sensation properties and its role in the discovery of the TRPM8 receptor. Here, we extend the SAFT-γ Mie group-contribution method to model cyclic alcohols, by introducing a new cCHOH group (c for cyclic) composed of two identical Mie segments. Three association sites (two electronic sites of type e and one hydrogen site of type H) are also included to mediate hydrogen bonding. New parameters that characterise the group interactions (one new like interaction and 26 new unlike interactions) are developed and are employed to determine the thermophysical properties (vapour pressure, saturation density, vaporisation enthalpy, and second-order thermodynamic derivative properties) of pure cyclic alcohols, and mixture properties (vapour–liquid equilibria, liquid–liquid equilibria, solid–liquid equilibria, density, and excess enthalpy) of cyclic alcohols in several solvents. The quality of the model is evaluated by comparing predictive calculations with experimental data of 76 systems: six pure fluids and 70 binary mixtures, selected from a large range of solvent families: cyclic, linear, and branched alkanes, 1-alcohols, 2-alcohols, 2-ketones, esters, aromatic compounds, water, and carbon dioxide. Very good overall agreement is found, including for the prediction of solid–liquid solubility, which confirms the transferability of the new group parameters. Together with previously developed parameters, these open the way for the prediction of the thermodynamic properties of further complex mixtures.

FTIR and GC-MS analyses of raw materials produced from food wastes used in synthesis of biofilms

The present study carried out the GC-MS and FTIR analyses of raw materials (ripe plantain peel powder, cassava starch, glycerol, acetic acid (vinegar) and eggshell powder) produced from food wastes that are used in production of biofilm. The GC-MS results revealed the presence of pentadecane, bis (2-methylpropyl) ester and benzoic acid, 3-(2-Hydroxy-6-methylphenyl)-4(3H)-quinazolinone). The FTIR analysis revealed 17 peaks for glycerol, 16 peaks for vinegar, 15 peaks for cassava starch, 16 peaks for eggshell; representing the functional groups of ether, ethene, amine, carboxylic acid, nitriles, methylene cyclic ester, primary, secondary and tertiary alcohols common to hydrocarbons. The presence of carboxylic acid was important for enhancing the mechanical and chemical properties of biofilms thereby making them viable alternatives to petroleum-based plastics. Amines contributed to the flexibility, strength, and thermal degradation resistance of biofilms, thus aiding in their biodegradability. In conclusion, the study showed that the raw materials possessed biological activities and their functional groups indicated that the raw materials are safe to humans and the environment.

C−H Bond Activation Facilitated by Nickel(II) Complexes Having Mighty Claws

AbstractStreamline synthesis of cyclic alcohols has been an enduring goal in synthetic chemistry. In this regard, a series of aminoquinoline‐based pincer ligands (L1(H)=2‐(dimethylamino)‐N‐(quinolin‐8‐yl)acetamide, L2(H)=2‐(diethylamino)‐N‐(quinoline‐8‐yl)acetamide, L3(H)=2‐(dipropylamino)‐N‐(quinoline‐8‐yl)acetamide and L4(H)=2‐(dibutylamino)‐N‐(quinolin‐8‐yl)acetamide)) and corresponding nickel(II) complexes of the type [Ni(L)Cl] (1–4) were synthesized and characterized using modern analytical techniques. Further, the catalytic activity of 1–4 was investigated for the oxidation of cyclohexane in the presence of different oxidants. All the catalysts showed substantial activity in the presence of m‐CPBA as the oxidant in DCM‐CH3CN (v/v, 3 : 1) solvent mixture at 60 ° C to yield cyclohexanol as the major product and cyclohexanone and caprolactone as the minor products. Under the optimised reaction conditions, catalytic activity was in the order 1 (936)>2 (892)>3 (835)>4 (785), which can be rationalized by the steric‐electronic properties of the respective ligands. Notably, with catalyst 1, we could achieve the highest TON (936) reported so far for cyclohexane oxidation using nickel(II) complexes having square planar geometry. The best catalyst, 1 was further used for the oxidation of other cycloalkanes and showed appreciable activity. The formation of chlorinated products in the reaction and product distribution pattern revealed that the oxidation is mediated majorly by 3‐chlorobenzoyloxy radical.

TBN as Organic Redox Cocatalyst for Oxidative Tiffeneau-Demjanov-Type Rearrangement Using O2 as Sole Oxidant.

The Tiffeneau-Demjanov-type rearrangement is a ring-expansion reaction involving the cationic rearrangement of cyclic alcohols. The carbocation intermediates can be generated in situ via various means, including Wacker oxidation. In near recent reports on the reinvestiagtions by Wahl et al. (Sietmann, J.; Tenberge, M.; Wahl, J. M. Wacker Oxidation of Methylenecyclobutanes: Scope and Selectivity in an Unusual Setting. Angew. Chem., Int. Ed. 2023, 62, e202215381) and Zhu et al. (Feng, Q.; Wang, Q.; Zhu, J.-P. Oxidative Rearrangement of 1,1-Disubstituted Alkenes to Ketones. Science 2023, 379, 1363-1368), stoichiometric oxidants were involved. In this work, we report the Tiffeneau-Demjanov-type rearrangement can be smoothly promoted by the Pd-TBN cocatalyzed aerobic Wacker oxidation using molecular oxygen as the sole oxidant. tert-Butanol is essential for achieving high yields. Since the first report by Grigg et al. in 1977 (Boontanonda, P.; Grigg, R. J. Palladium (II)-Catalysed Ring Expansion of Methylenecyclobutanes and Related Systems. J. Chem. Soc. Chem. Commun. 1977, 17, 583-584), the five-decade journey of Pd-catalyzed Tiffeneau-Demjanov-type rearrangement returns to the aerobic again.

Soft confinement of water in aliphatic alcohols: MIR/NIR spectroscopic and DFT studies

Here, we present the first examination of the state of water under a soft confinement in eight aliphatic alcohols including cyclopentanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-decanol, 2-octanol and 3-octanol. Due to relatively large size of the aliphatic part, water has limited solubility in all studied alcohols. Water content in saturated solutions was determined by Karl Fischer titration and correlated with the spectroscopic data. This way, we determined the molar absorptivity of the ν2+ν3 combination mode. The effect of addition of water and temperature variation was monitored by ATR-IR and NIR spectroscopy. Analysis of the experimental results was guided by DFT calculations, which provided the structures, harmonic MIR spectra and binding energies of selected alcohol-water complexes.Our studies demonstrated that the state of water in alcohols is related to its solubility, which depends on structure of solvent molecules. The solubility of water in 1-alcohols decreases on increasing of the chain length, but for long chain alcohols this effect is less evident. More apparent solubility reduction appears in going from the primary to secondary alcohols. The effective shielding of the OH group in the linear alcohols is achieved when on both sides of the OH group are ethyl or longer substituents, while the shielding by methyl groups is less efficient. Water is much better soluble in the cyclic alcohols as compared with the linear ones due to better accessibility of the OH group.The soft confinement of water in aliphatic alcohols allows for flexible structural arrangements and interactions. Even at low water content, we did not observe free molecules of water. At these conditions, the molecules of water are singly or doubly bonded to the OH groups from the alcohol. Increasing solubility of water reduces the number of the free OH groups and leads to formation of water clusters. Obtained results allow concluding that in alcohols with sizable aliphatic part the molecules of water are confined in the vicinity of the OH groups.

URJC-1: Stable and Efficient Catalyst for O-Arylation Cross-Coupling.

The design of metal-organic frameworks (MOFs) allows the definition of properties for their final application in small-scale heterogeneous catalysis. Incorporating various catalytic centers within a single structure can produce a synergistic effect, which is particularly intriguing for cross-coupling reactions. The URJC-1 material exhibits catalytic duality: the metal centers act as Lewis acid centers, while the nitrogen atoms of the organic ligand must behave as basic centers. The impact of reaction temperature, catalyst concentration, and basic agent concentration was evaluated. Several copper-based catalysts, including homogeneous and heterogeneous MOF catalysts with and without the presence of nitrogen atoms in the organic ligand, were assessed for their catalytic effect under optimal conditions. Among the catalysts tested, URJC-1 exhibited the highest catalytic activity, achieving complete conversion of 4-nitrobenzaldehyde with only 3% mol copper concentration in one hour. Furthermore, URJC-1 maintained its crystalline structure even after five reaction cycles, demonstrating remarkable stability in the reaction medium. The study also examined the impact of various substituents of the substrate alcohol on the reaction using URJC-1. The results showed that the reaction had high activity when activating substituents were present and for most cyclic alcohols rather than linear ones.

The Synergy of Alloyed Pd and Ni Over H-NbOx: Enhancing Hydrogenation of Lignin Derivatives and Lignin Bio-Oil into Cyclic Hydrocarbons and Alcohols

The Synergy of Alloyed Pd and Ni Over H-NbO_<i>x</i>: Enhancing Hydrogenation of Lignin Derivatives and Lignin Bio-Oil into Cyclic Hydrocarbons and Alcohols

Production of high-carbon-number naphthenes for bio-aviation fuels from bio-crude prepared by fast pyrolysis of lignocellulose

Lignocellulose has been suggested as a cost-effective, environmentally sustainable substitute for paraffins, aromatics, and naphthenes in aviation fuel. However, bio-crude derived from the fast pyrolysis of lignocellulose poses challenges because of its high acidity and viscosity arising from oxygenates and water; in addition, the low-carbon-number hydrocarbons obtained from lignocellulose-derived sugars and phenols are unsuitable for aviation fuels. In this investigation, high-carbon-number hydrocarbon fuels are generated from bio-crude through condensation reactions between phenols and saturated cyclic alcohols, achieving a heavy fraction similar to that of aviation fuels. The one-pass, four-step continuous-flow reaction of bio-crude is conducted using a catalysis reactor equipped with carbon-supported palladium, titania-supported nickel–iron, hydrogen-form zeolite Y, and tungstate–zirconia-supported ruthenium. In contrast with conventional two-step hydrodeoxygenation methods yielding 1.1% dimeric cycloalkanes, the suggested multi-step reaction produced 4.5 to 4.7% yields of heavier naphthenes containing twelve or more carbon atoms.

Organic Synthesis Away from Equilibrium: Contrathermodynamic Transformations Enabled by Excited-State Electron Transfer.

ConspectusChemists have long been inspired by biological photosynthesis, wherein a series of excited-state electron transfer (ET) events facilitate the conversion of low energy starting materials such as H2O and CO2 into higher energy products in the form of carbohydrates and O2. While this model for utilizing light-driven charge transfer to drive catalytic reactions thermodynamically "uphill" has been extensively adapted for small molecule activation, molecular machines, photoswitches, and solar fuel chemistry, its application in organic synthesis has been less systematically developed. However, the potential benefits of these approaches are significant, both in enabling transformations that cannot be readily achieved using conventional thermal chemistry and in accessing distinct selectivity regimes that are uniquely enabled by excited-state mechanisms. In this Account, we present work from our group that highlights the ability of visible light photoredox catalysis to drive useful organic transformations away from their equilibrium positions, addressing a number of long-standing synthetic challenges.We first discuss how excited-state ET enabled the first general methods for the catalytic anti-Markovnikov hydroamination of unactivated alkenes with alkyl amines. In these reactions, an excited-state iridium(III) photocatalyst reversibly oxidizes secondary amine substrates to their corresponding aminium radical cations (ARCs). These electrophilic N-centered radicals can then react with olefins to furnish valuable tertiary amine products with complete anti-Markovnikov regioselectivity. Notably, some of these products are less thermodynamically stable than their corresponding amine and alkene starting materials. We next present a strategy for light-driven C-C bond cleavage within various aliphatic alcohols mediated by homolytic activation of alcohol O-H bonds by excited-state proton-coupled electron transfer (PCET). The resulting alkoxy radical intermediates then undergo C-C β-scission to ultimately provide isomeric linear carbonyl products that are often higher in energy than their cyclic alcohol precursors. Applications of this chemistry for the light-driven depolymerization of lignin biomass, commercial phenoxy resin, hydroxylated polyolefin derivatives, and thermoset polymers are presented as well. We then describe a method for the contrathermodynamic positional isomerization of highly substituted olefins by means of cooperative photoredox and chromium(II) catalysis. In this work, generation of an allylchromium(III) species that can undergo highly regioselective in situ protodemetalation enables access to a less substituted and thermodynamically less stable positional isomer. Product selectivity in this reaction is determined by the large differential in oxidation potentials between differently substituted olefin isomers. Lastly, we discuss a light-driven deracemization reaction developed in collaboration with the Miller group, wherein a racemic urea substrate undergoes spontaneous optical enrichment upon visible light irradiation in the presence of an iridium(III) chromophore, a chiral Brønsted base, and a chiral peptide thiol. Excellent levels of enantioselectivity are achieved via sequential and synergistic proton transfer (PT) and H atom transfer (HAT) steps. Taken together, these examples highlight the ability of excited-state ET events to enable access to nonequilibrium product distributions across a wide range of catalytic, redox-neutral transformations in which photons are the only stoichiometric reagents.

Photoelectrochemical Fe/Ni cocatalyzed C−C functionalization of alcohols

The simultaneous activation of reactants on the anode and cathode via paired electrocatalysis has not been extensively demonstrated. This report presents a paired oxidative and reductive catalysis based on earth-abundant iron/nickel cocatalyzed C–C functionalization of ubiquitous alcohols. A variety of alcohols (i.e., primary, secondary, tertiary, or unstrained cyclic alcohols) can be activated at very low oxidation potential of (~0.30 V vs. Ag/AgCl) via photoelectrocatalysis coupled with versatile electrophiles. This reactivity yields a wide range of structurally diverse molecules with broad functional group compatibility (more than 50 examples).

Al(OiPr)3 as an effective catalyst for the enhancement of Meerwein−Ponndorf−Verley (MPV) reductions of Morita-Baylis-Hillman (MBH) cyclic alcohols

Carbonyl reductions using NaBH4 are generally high-yielding and highly selective processes commonly used in organic synthesis and the pharmaceutical industry. However, the reaction is exothermic, and the stability of the NaBH4 solution is limited, resulting in long reaction times. In this work, efficient reductions of MBH alcohols with CeCl3/NaBH4 in MeOH are reported . Furthemore in this method, aluminum isopropoxide and isobutanol are employed as proton sources in a transfer process. This approach exhibits impressive selectivity and high yields, resulting in the desired formation of bidentate allylic alcohol.

SilE-R and SilE-S-DABB Proteins Catalying Enantiospecific Hydrolysis of Organosilyl Ethers.

Silyl ethers fulfil a fundamental role in synthetic organic chemistry as protecting groups and their selective cleavage is an important factor in their application. We present here for the first time two enzymes, SilE-R and SilE-S, which are able to hydrolyse silyl ethers. They belong to the stress-response dimeric A/B barrel domain (DABB) family and are able to cleave the Si-O bond with opposite enantiopreference. Silyl ethers containing aromatic, cyclic or aliphatic alcohols and, depending on the alcohol moiety, silyl functions as large as TBDMS are accepted. The X-ray crystal structure of SilE-R, determined to a resolution of 1.98 Å, in combination with mutational studies, revealed an active site featuring two histidine residues, H8 and H79, which likely act synergistically as nucleophile and Brønsted base in the hydrolytic mechanism, which has not previously been described for enzymes. Although the natural function of SilE-R and SilE-S is unknown, we propose that these 'silyl etherases' may have significant potential for synthetic applications.

Kinetic Resolution of Cyclic Tertiary Alcohols with Lipase A from Candida Antarctica

AbstractEnzyme‐catalyzed acylative kinetic resolution (KR) and dynamic kinetic resolution (DKR) of racemic primary and secondary alcohols have been widely reported to produce esters with high enantiomeric purity. In contrast, similar KRs of tertiary alcohols have been reported for only a limited range of substrates and require prolonged reaction times of several days. To gain deeper insight into the substrate scope and increase the process efficiency, we examined the reaction conditions using commercially available immobilized lipase A from Candida antarctica and found that the addition of the heterogeneous, inorganic base sodium carbonate significantly increased the reaction rate while maintaining high enantioselectivity. The use of vinyl hexanoate as the acyl donor provided esters that were stable during chromatography purification. The optimized reaction conditions were then successfully applied to a range of cyclic tertiary alcohols containing tetralin, dihydroindene, chromane, and thiochromane skeletons having, in part, a substituent on the aromatic ring. In this study on the structure–reactivity relationship of enzymatic KR‐type reactions, we achieved &gt;30 % conversion for various tertiary alcohols in 24 h at 25 °C, producing optically active esters with 88–99 % ee.

Development of Efficient Synthetic Reactions Using Enamines and Enamides Carrying Oxygen Atom Substituent on Nitrogen Atom.

We have developed efficient synthetic reactions using enamines and enamides carrying oxygen atom substituent on nitrogen, such as N-alkoxyenamines, N,α-dialkoxyenamines, N-alkoxyanamides, and N-(benzoyloxy)enamides. The umpolung reaction by polarity inversion at the β-position of N-alkoxyenamines afforded α-alkyl-, α-aryl-, α-alkenyl-, and α-heteroarylketones by using aluminum reagent as nucleophiles. Furthermore, one-pot umpolung α-phenylation of ketones has been also developed. We applied this method to umpolung reaction of N,α-dialkoxyenamine, generated from N-alkoxyamide to afford α-arylamides. The vicinal functionalization of N-alkoxyenamines has been achieved with the formation of two new carbon-carbon bonds by using an organo-aluminum reagent and subsequent allyl magnesium bromide or tributyltin cyanide. A sequential retro-ene arylation has been developed for the conversion of N-alkoxyenamides to the corresponding tert-alkylamines. The [3,3]-sigmatropic rearrangement of N-(benzoyloxy)enamides followed by arylation afforded cyclic β-aryl-β-amino alcohols bearing a tetrasubstituted carbon center. The resulting products were converted into the corresponding sterically congested cyclic β-amino alcohols, as well as the dissociative anesthetic agent Tiletamine.

Comparison of apoptotic effects of lupeol on A549 and C6 cell lines

Lupeol compound is a cyclic triterpene alcohol that is widely found in plants. The compound lupeol has been reported to exhibit antitumor, anti-inflammatory, anxiolytic, neuroprotective and hepatoprotective effects. Recent research shows that lupeol could be a potential medicine for various diseases and also an adjuvant for intractable diseases. Cancer poses a health threat that is increasingly common around the world. Among new cancer cases, lung cancer is one of the most common and deadly cancers worldwide. In this study, the anticancer efficiency of lupeol on human lung adenocarcinoma A549 and glioma C6 cell lines were examined. Various concentrations of lupeol (500, 250, 125, 62.5, 31.25, 15.62, 7.81, 3.90 μM) effectually reduced cell viability in the A549 and C6 cell lines in a dose-dependent manner. These results showed that lupeol had selective anticancer activity against A549 and C6 cell lines.

Electrochemical Azo-free Mitsunobu-type Reaction.

The classic chemical Mitsunobu reaction suffers from the need of excess alcohol activation reagents and the generation of significant by-products. Efforts to overcome these limitations have resulted in numerous creative solutions, but the substrate scope of these catalytic processes remains limited. Here we report an electrochemical Mitsunobu-type reaction, which features azo-free alcohol activation and broad substrate scope. This user-friendly technology allows a vast collection of heterocycles as the nucleophile, which can couple with a series of chiral cyclic and acyclic alcohols in moderate to high yields and excellent ee's. This practical reaction is scalable, chemoselective, uses simple Electrasyn setup with inexpensive electrodes and requires no precaution to exclude air and moisture. The synthetic utility is further demonstrated on the structural modification of diverse bioactive natural products and pharmaceutical derivatives and its straightforward application in a multiple-step synthesis of a drug candidate.

Electrochemical Azo‐free Mitsunobu‐type Reaction

AbstractThe classic chemical Mitsunobu reaction suffers from the need of excess alcohol activation reagents and the generation of significant by‐products. Efforts to overcome these limitations have resulted in numerous creative solutions, but the substrate scope of these catalytic processes remains limited. Here we report an electrochemical Mitsunobu‐type reaction, which features azo‐free alcohol activation and broad substrate scope. This user‐friendly technology allows a vast collection of heterocycles as the nucleophile, which can couple with a series of chiral cyclic and acyclic alcohols in moderate to high yields and excellent ee's. This practical reaction is scalable, chemoselective, uses simple Electrasyn setup with inexpensive electrodes and requires no precaution to exclude air and moisture. The synthetic utility is further demonstrated on the structural modification of diverse bioactive natural products and pharmaceutical derivatives and its straightforward application in a multiple‐step synthesis of a drug candidate.

Facile one-pot synthesis of niobium-containing carbon nitride and the catalytic application for synthesis of dimethyl carbonate

Dimethyl carbonate (DMC) is a building block in wide chemical-related fields and the transesterification of ethylene carbonate (EC) and methanol/ethanol is a sustainable route for the synthesis of DMC. Herein, in order to explore efficient heterogeneous catalysts, niobium-containing carbon nitride materials were synthesized by a convenient one-pot calcination method. By reserving the main chemical functionalities of carbon nitride, the Nb-CN composites contained both acidic and basic properties, and Nb can be dispersed by carbon nitride. In the transesterification of EC with methanol, under the reaction temperature of 140 °C and reaction time of 4 h, the conversion of EC and the selectivity of DMC reached 53.8% and 100%, respectively, and the activity of the catalyst did not decrease significantly after several recycling runs. Furthermore, the Nb-CN could promote transesterification reactions of other cyclic carbonate and alcohols.