Sébastien Tilloy

Cyclodextrins as Mass Transfer Additives in Aqueous Organometallic Catalysis

During the past fifteen years, the use of chemically modified cyclodextrins (CDs) in aqueous organometallic catalysis has sig- nificantly contributed to enlarge the application field of biphasic processes in chemistry. In this paper, we describe how these su- pramolecular receptors became one of the most efficient solutions to solve mass transfer problems in aqueous organometallic catalysis. The scientific gaps that have been cleared to explain the exact role of the CDs in these biphasic systems are especially emphasized. In particular, the impact of supramolecular interactions between chemically modified CDs and substrates, water soluble ligands or or- ganometallic catalysts is addressed for a better understanding of the recognition processes involved in the catalytic reactions.

Comparative Raman spectroscopy study of sulfonate-substituted triphenylphosphines

Abstract A comparative Raman spectroscopy study of triphenylphosphine (TPP), monosulfonated triphenylphosphine (TPPMS) and trisulfonated triphenylphosphine (TPPTS) is reported. The characteristic modes for each molecule were evidenced and we suggest assignments for the majority of the modes. A detailed study of the phenyl breathing mode (around 1000 cm−1) shows that in the case of TPP, the three rings are nonequivalent, whereas for TPPTS, the sulfonate substituant seems to contribute to stabilise the molecule structure so as the rings are equivalent. The TPPMS spectrum is a medium case between the extreme cases of TPP and TPPTS and presents the characteristics of the two previous spectra.

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. As macrophages are widely described as the major cell type forming the foam cells by accumulating intracellular cholesterol, RCT alterations have been poorly studied at the arterial endothelial cell and SMC levels. Amongst the therapeutics tested to actively counteract cellular cholesterol accumulation, the methylated β-cyclodextrin, KLEPTOSE® CRYSMEβ, has recently shown promising effects on decreasing the atherosclerotic plaque size in atherosclerotic mouse models. Therefore we investigated in vitro the RCT process occurring in SMCs and in arterial endothelial cells (ABAE) as well as the ability of some modified β-CDs with different methylation degree to modify RCT in these cells. To this aim, cells were incubated in the presence of different methylated β-CDs, including KLEPTOSE® CRYSMEβ. Both cell types were shown to express basal levels of ABCA1 and SR-BI whereas ABCG1 was solely found in ABAE. Upon CD treatments, the percentage of membrane-extracted cholesterol correlated to the methylation degree of the CDs independently of the lipid composition of the cell membranes. Decreasing the cellular cholesterol content with CDs led to reduce the expression levels of ABCA1 and ABCG1. In addition, the cholesterol efflux to ApoA-I and HDL particles was significantly decreased suggesting that cells forming the blood vessel wall are able to counteract the CD-induced loss of cholesterol. Taken together, our observations suggest that methylated β-CDs can significantly reduce the cellular cholesterol content of cells forming atherosclerotic lesions and can subsequently modulate the expression of ABC transporters involved in RCT. The use of methylated β-CDs would represent a valuable and efficient tool to interfere with atherosclerosis pathogenesis in patients, nonetheless their mode of action still needs further investigations to be fully understood and finely controlled at the cellular level.

Robust Mesoporous CoMo/γ-Al2O3 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. In this work, we describe two different synthetic routes (i.e., impregnation and cyclodextrin-assisted one-pot colloidal approach), for the preparation in aqueous phase of six high surface area CoMo/γ-Al2O3 catalysts. Catalytic tests performed on the HTL of Nannochloropsis gaditana microalga indicate that solids prepared by the one-pot colloidal approach show higher hydrothermal stability and enhanced biocrude yield with respect to the catalyst-free test. The positive effect of the substitution of the block copolymer Tetronic T90R4 for Pluronic F127 in the preparation procedure was evidenced by diffuse reflectance UV-visible spectroscopy, X-ray diffraction, N2-adsorption-desorption, and H2-temperature-programmed reduction measurements and confirmed by the higher quality of the obtained biocrude, which exhibited lower oxygen content and higher-energy recovery equal to 62.5% of the initial biomass.

Ring opening polymerization of ε-caprolactone in the presence of wet β-cyclodextrin: effect of the operative pressure and of water molecules in the β-cyclodextrin cavity

The ring opening polymerization (ROP) of e-caprolactone (CL) in the presence of β-cyclodextrin (β-CD) was performed in batch reactors both at room pressure and with the reaction system pressurized with CO2, N2 or Ar. Significant enhancements of the polymerization rate was observed when the ROP was carried out with wet β-CD under pressure. For example, after 24 hours at 120 °C with a β-CD/CL molar ratio of about 1/100, the monomer conversion increased from 4 to 98–99% when the pressure was changed from 0.1 to 12.5–13.0 MPa independent of the nature of the compressing gas. MALDI-TOF analyses indicated that a major fraction of polymer chains obtained in pressurized systems was initiated by water molecules. The collected results suggest that at 12–13 MPa wet β-CD can catalyse both the ring opening of e-caprolactone and the polymerization of the obtained linear species and that high energy water molecules located inside the cavity of the cyclic oligosaccharide must play a role in initiating the polymerization. The trend of number average molecular weight and the results of MALDI-TOF analyses obtained in polymerizations performed for long reaction times and in a hydrolysis test of commercial poly(e-caprolactone) indicate that wet β-CD can work as an artificial lipase enzyme under the adopted conditions.

Water-soluble phosphane-substituted cyclodextrin as an effective bifunctional additive in hydroformylation of higher olefins

In cyclodextrin (CD)-mediated aqueous biphasic catalysis, favoring contacts between the CD (“host”), the organic substrate (“guest”) and the water-soluble catalyst is crucial for the reaction to proceed efficiently at the aqueous/organic interface. Grafting the catalyst onto the CD backbone thus appears as an attractive approach to favor the molecular recognition of the substrate and its subsequent catalytic conversion into products. In this context, a new water-soluble β-CD-based phosphane was synthesized and characterized by NMR, tensiometric and ITC measurements. The β-CD-based phosphane consisted of a 3,3′-disulfonatodiphenyl phosphane connected to the primary face of β-CD by a dimethyleneamino spacer. Intra- and intermolecular inclusion processes of one of the two sulfophenyl groups into the β-CD cavity were identified in water. However, the association constant (Ka) related to the β-CD/sulfophenyl group couple was low. Accordingly, the inclusion process was easily displaced upon coordination to rhodium complexes. The efficacy of the resulting Rh-complex coordinated by β-CD-based phosphanes was assessed in Rh-catalyzed hydroformylation of higher olefins. The catalytic system proved to be far more successful and efficient than a system consisting of supramolecularly interacting phosphanes and CDs. The catalytic activity was up to 30-fold higher while the chemo- and regioselectivities remain rather unchanged.

Unconventional media and technologies for starch etherification and esterification

Among the most widespread starch derivatives, etherified and esterified starches play an important role. These derivatives are generally prepared by using thermal energy and conventional solvents. This review summarizes the recent advancements in the etherification and esterification of starch in unconventional media, i.e. ionic liquids or supercritical CO2, and by employing unconventional technologies, i.e. microwaves, ultrasounds or ball-milling. The present contribution aims to provide an overview to help researchers seeking an alternative medium or technology to functionalize starch. The green aspects of unconventional approaches are presented and the physical-chemical properties of modified starches obtained by these approaches are also described. Whenever possible, the advantages and disadvantages of each system are discussed. Finally, even if it is not always mentioned in the publications, the use of these experimental conditions probably leads to a partial degradation of the starch molecular structure.