Rhodium/Trialkylamines Catalyzed Reductive Hydroformylation in Ionic Liquid/Heptane Medium: An Unexpected Concept for Catalyst Recycling in Batch and Continuous Flow Processes.

We report here the rhodium catalyzed reductive hydroformylation of methyl 10-undecenoate. Our approach is based on an ionic liquid/heptane biphasic system associated with commercially available trialkylamines. The effects of various reaction parameters such as amine type, amine amount, temperature, syngas pressure and composition were studied in order to minimize the rhodium leaching and increase the production of primary alcohols.

Stereoisomers Are Not Machine Learning's Best Friends.

This study addresses the challenge of accurately identifying stereoisomers in cheminformatics, which originates from our objective to apply machine learning to predict the association constant between cyclodextrin and a guest. Identifying stereoisomers is indeed crucial for machine learning applications. Current tools offer various molecular descriptors, including their textual representation as Isomeric SMILES that can distinguish stereoisomers.

Unnatural cyclodextrins can be accessed from enzyme-mediated dynamic combinatorial libraries.

Dynamic systems of cyclodextrins (CDs) enabled by a native cyclodextrin glucanotransferase (CGTase) can incorporate unnatural glucopyranose-derived building blocks, expanding the applicability of enzyme-mediated dynamic combinatorial chemistry by using synthetically modified substrates. Starting dynamic combinatorial libraries from CDs with a single 6-modified glucopyranose results in a dynamic mixture of CDs containing several modified glucopyranoses. The relative concentrations of modified α, β or γ-CDs can be controlled by the addition of templates, providing a novel way to access modified CDs.

Reductive Hydroformylation of Isosorbide Diallyl Ether.

Isosorbide and its functionalized derivatives have numerous applications as bio-sourced building blocks. In this context, the synthesis of diols from isosorbide diallyl ether by hydrohydroxymethylation reaction is of extreme interest. This hydrohydroxymethylation, which consists of carbon-carbon double bonds converting into primary alcohol functions, can be obtained by a hydroformylation reaction followed by a hydrogenation reaction.

Multiscale Structure of Starches Grafted with Hydrophobic Groups: A New Analytical Strategy.

Starch, an abundant and low-cost plant-based glucopolymer, has great potential to replace carbon-based polymers in various materials. In order to optimize its functional properties for bioplastics applications chemical groups need to be introduced on the free hydroxyl groups in a controlled manner, so an understanding of the resulting structure-properties relationships is therefore essential. The purpose of this work was to study the multiscale structure of highly-acetylated (degree of substitution, 0.

New Lipidyl-Cyclodextrins Obtained by Ring Opening of Methyl Oleate Epoxide Using Ball Milling.

Bearing grafts based on fatty esters derivatives, lipidyl-cyclodextrins (L-CDs) are compounds able to form water-soluble nano-objects. In this context, bicatenary biobased lipidic-cyclodextrins of low DS were easily synthesized from a fatty ester epoxide by means of alternative methods (ball-milling conditions, use of enzymes). The ring opening reaction of methyl oleate epoxide needs ball-milling and is highly specific of cyclodextrins in solventless conditions.

Robust Mesoporous CoMo/γ-AlO Catalysts from Cyclodextrin-Based Supramolecular Assemblies for Hydrothermal Processing of Microalgae: Effect of the Preparation Method.

Hydrothermal liquefaction (HTL) is a promising technology for the production of biocrude oil from microalgae. Although this catalyst-free technology is efficient under high-temperature and high-pressure conditions, the biocrude yield and quality can be further improved by using heterogeneous catalysts. The design of robust catalysts that preserve their performance under hydrothermal conditions will be therefore very important in the development of biorefinery technologies.

Transition Metal Complexes Coordinated by Water Soluble Phosphane Ligands: How Cyclodextrins Can Alter the Coordination Sphere?

The behaviour of platinum(II) and palladium(0) complexes coordinated by various hydrosoluble monodentate phosphane ligands has been investigated by P{¹H} NMR spectroscopy in the presence of randomly methylated β-cyclodextrin (RAME-β-CD). This molecular receptor can have no impact on the organometallic complexes, induce the formation of phosphane low-coordinated complexes or form coordination second sphere species. These three behaviours are under thermodynamic control and are governed not only by the affinity of RAME-β-CD for the phosphane but also by the phosphane stereoelectronic properties.

Cyclodextrins as Emerging Therapeutic Tools in the Treatment of Cholesterol-Associated Vascular and Neurodegenerative Diseases.

Cardiovascular diseases, like atherosclerosis, and neurodegenerative diseases affecting the central nervous system (CNS) are closely linked to alterations of cholesterol metabolism. Therefore, innovative pharmacological approaches aiming at counteracting cholesterol imbalance display promising therapeutic potential. However, these approaches need to take into account the existence of biological barriers such as intestinal and blood-brain barriers which participate in the organ homeostasis and are major defense systems against xenobiotics.

β-Cyclodextrins Decrease Cholesterol Release and ABC-Associated Transporter Expression in Smooth Muscle Cells and Aortic Endothelial Cells.

Atherosclerosis is an inflammatory disease that leads to an aberrant accumulation of cholesterol in vessel walls forming atherosclerotic plaques. During this process, the mechanism regulating complex cellular cholesterol pools defined as the reverse cholesterol transport (RCT) is altered as well as expression and functionality of transporters involved in this process, namely ABCA1, ABCG1, and SR-BI. Macrophages, arterial endothelial and smooth muscle cells (SMCs) have been involved in the atherosclerotic plaque formation.

Synthesis and characterization of a new photoinduced switchable β-cyclodextrin dimer.

This paper reports an efficient preparation of bridged bis-β-CD AZO-CDim 1 bearing azobenzene as a linker and exhibiting high solubility in water. The photoisomerization properties were studied by UV-vis and HPLC and supported by ab initio calculations. The cis/trans ratio of AZO-CDim 1 is 7:93 without irradiation and 37:63 after 120 min of irradiation at 365 nm; the reaction is reversible after irradiation at 254 nm.

A cyclodextrin dimer as a supramolecular reaction platform for aqueous organometallic catalysis.

A reaction platform based on a cyclodextrin dimer, which is able to simultaneously include a substrate in one cavity and an organometallic catalyst into the other, proved to be highly efficient for aqueous hydroformylation reaction of higher olefins.

Hydroformylation in aqueous biphasic media assisted by molecular receptors.

The role of molecular receptors in aqueous biphasic hydroformylation of higher olefins is highlighted through a detailed analysis of their molecular recognition properties. The behavior of cyclodextrins and calixarenes as molecular receptors is especially emphasized and discussed. Their supramolecular interactions with the substrates and the water-soluble ligands proved to be an essential parameter guiding the reaction performances.

Phosphane-based cyclodextrins as mass transfer agents and ligands for aqueous organometallic catalysis.

The replacement of hazardous solvents and the utilization of catalytic processes are two key points of the green chemistry movement, so aqueous organometallic catalytic processes are of great interest in this context. Nevertheless, these processes require not only the use of water-soluble ligands such as phosphanes to solubilise the transition metals in water, but also the use of mass transfer agents to increase the solubility of organic substrates in water. In this context, phosphanes based on a cyclodextrin skeleton are an interesting alternative since these compounds can simultaneously act as mass transfer agents and as coordinating species towards transition metals.

Carboxylated polymers functionalized by cyclodextrins for the stabilization of highly efficient rhodium(0) nanoparticles in aqueous phase catalytic hydrogenation.

Rhodium(0) nanoparticles stabilized by a polymer containing carboxylate and β-cyclodextrin moieties have high stability and catalytic activity for aqueous hydrogenation reactions of olefins and aromatic substrates. This catalytic system can be recycled and reused without loss of activity. These high catalytic performances can be attributed to conjugated electrostatic interactions (carboxylate groups) and steric interactions (polymer structure and β-cyclodextrin moiety).

Aqueous biphasic hydroformylation in the presence of cyclodextrins mixtures: evidence of a positive synergistic effect.

Mixtures of randomly methylated cyclodextrins of various sizes have been evaluated in the rhodium-catalysed hydroformylation of higher olefins in an aqueous biphasic medium. A marked positive non-linear effect on 1-tetradecene conversion is observed when the CD molar ratio in the mixture is modified. The formation of 2:1 ternary inclusion complexes between RAME-CDs and the olefin is supposed to be responsible for the extra conversion observed.

Cyclodextrin-phosphane possessing a guest-tunable conformation for aqueous rhodium-catalyzed hydroformylation.

The inclusion of a guest inside the cavity of a new water-soluble cyclodextrin-phosphane allows controlling the natural conformation of this ligand leading to an inversion of the regioselectivity during aqueous hydroformylation reaction.

New phosphane based on a beta-cyclodextrin, exhibiting a solvent-tunable conformation, and its catalytic properties.

A new diphenylphosphane based on a beta-cyclodextrin skeleton that exhibits a dual solubility in water and in organic solvent was synthesised. Interestingly, a solvent-dependent conformation change was evidenced by NMR spectroscopy studies; the self-inclusion of a phenyl group of the phosphane moiety into cyclodextrin cavity observed in water disappeared in organic solvents due to a change in conformation. Hydrogenation or hydroformylation reactions performed in water and in organic solvents showed that this ligand was able to stabilise catalytically active rhodium species in solution.

A property-matched water-soluble analogue of the benchmark ligand PPh3.

A series of sulfonated biphenylphosphanes were readily prepared from commercially available, inexpensive, and air-stable organic compounds. Of these, the trisulfonated trisbiphenylphosphane can be considered as a true water-soluble analogue of PPh(3) as the cone angle and basicity of both phosphanes are very close and result in a similar coordination mode on palladium and rhodium complexes. The catalytic performance of the trisulfonated trisbiphenylphosphane was evaluated in the aqueous hydroformylation of 1-decene and the Tsuji-Trost reaction.

Complexation of phosphine ligands with peracetylated beta-cyclodextrin in supercritical carbon dioxide: spectroscopic determination of equilibrium constants.

The interaction between peracetylated beta-cyclodextrin and several triphenyl phosphine derivatives was studied in supercritical carbon dioxide (scCO2) by UV-visible spectroscopy. The equilibrium constant for a 1:1 complexation reaction was obtained from titration spectra and calculated using two established mathematical models. The values of the equilibrium constants are 1-3 orders of magnitude smaller than those obtained in aqueous solution with analogous phosphines.

Biphasic aqueous organometallic catalysis promoted by cyclodextrins: can surface tension measurements explain the efficiency of chemically modified cyclodextrins?

Methylated and hydroxypropylated cyclodextrins (CDs) are highly efficient mass transfer promoters in biphasic aqueous organometallic processes. The surface tension measurements demonstrated that these CDs adsorb at air-water interface and allowed to determine surface excess of CD by using Gibbs adsorption equation. Interestingly, a good correlation between surface excess and catalytic activity was obtained in the case of hydroformylation and Tsuji-Trost reactions.

Methylated beta-cyclodextrin as P-gp modulators for deliverance of doxorubicin across an in vitro model of blood-brain barrier.

Co-incubations of various beta-cyclodextrins and doxorubicin have been evaluated on an in vitro model of blood-brain barrier in order to increase the delivery of this P-gp substrate to the brain. Among these cyclodextrins used, the Rame-beta-cyclodextrin and Crysme-beta-cyclodextrin increased the transport by a factor of 2 and 3.7, respectively.

Rhodium complexes non-covalently bound to cyclodextrins: novel water-soluble supramolecular catalysts for the biphasic hydroformylation of higher olefins.

A new class of cationic alpha-cyclodextrins bearing 2-hydroxy-3-trimethylammoniopropyl groups has been synthesised. We investigated their efficiency as mass-transfer promoters in a biphasic hydroformylation reaction catalysed by a rhodium trisulfonated triphenylphosphine system. These cationic alpha-cyclodextrins greatly increased the reaction rate, the chemoselectivity, and, surprisingly, the linear-to-branched aldehyde ratio.

Adamantoylated monosaccharides: new compounds for modification of the properties of cyclodextrin-containing materials.

Adamantoyl glycosides were obtained in good yields by coupling adamantanecarboxylic acid with monosaccharides. They form very stable inclusion complexes with beta-cyclodextrin, as shown by (1)H NMR measurements.