"Un nouveau ligand dérivé du binol : le (R)-6,6'- bis (trifluorométhanesulfonyl) -1,1'-bi2-naphtol. Synthèse et applications en catalyse asymétrique"

BINOL is an efficient chiral ligand widely used in asymmetric reactions. The work of this thesis concerns the synthesis of a new derivative of BINOL, bearing a triflyl group (CF3SO2) one of the strongest electron withdrawing groups and demonstrates its first applications in asymmetric catalysis.The first part constitutes a bibliographic review on BINOL and its derivatives substituted by electron withdrawing groups in position 3,3' and/or 6,6'. These latter ligands have shown that the presence of this type of group induces strong increases in stereoselectivity and is beneficial for turnover.The second part presents the synthesis and the characterization of the new (R)-6,6'-bis(trifluorométhanesulfonyl)-1,1'-bi-2-naphthol. Due to the difficulty of the aromatic trifluoromethanesulfonylation, this synthesis has required numerous attempts which we examined before detailing the original route to this ligand that we developed.The third part describes the first applications of (R)-6,6'-Tf2BINOL in asymmetric catalysis. The results that we have obtained clearly indicate that this ligand, complexed with oxophilic metals such as zirconium or titanium leads to very active organometallic catalysts.During the characterization and tests of crystallization of the zirconium complex, we isolated a product of which the structure corresponds to an organometallic cluster. This proved to be air-stable and more powerful in the catalysis of the Mannich-type reactions than the complex prepared in situ.Le BINOL est un inducteur chiral largement utilisé dans les réactions asymétriques. Le travail de ce mémoire porte sur la synthèse d'un nouveau dérivé du BINOL, porteur de groupements triflyles (CF3SO2) fortement électroattracteurs et présente ses premières applications en catalyse asymétrique.La première partie constitue une mise au point bibliographique sur le BINOL et ses dérivés substitués par des groupements électroattracteurs en position 3,3' et/ou 6,6'. Ces derniers ont montré que la présence de ce type de groupements induit de fortes augmentations de stéréosélectivité et s'est révélée bénéfique pour le turnover.La deuxième partie présente la synthèse et la caractérisation du nouveau (R)-6,6'–bis(trifluorométhanesulfonyl)-1,1'-bi-2-naphtol. Au regard de la difficulté de la trifluorométhanesulfonylation aromatique, cette synthèse a nécessité de nombreuses tentatives que nous citons avant de détailler la voie de synthèse originale de ce ligand que nous avons mise au point.La troisième partie décrit les premières applications du (R)-6,6'-Tf2BINOL en catalyse asymétrique. Les résultats que nous avons obtenus indiquent clairement que ce ligand, complexé à des métaux oxophiles tels que le zirconium ou le titane, conduit à des catalyseurs organométalliques très actifs.Lors de la caractérisation et des essais de cristallisation du complexe du zirconium, nous avons isolé un produit dont la structure correspond à un cluster organométallique. Ce dernier s'est avéré stable à l'air et plus performant dans la catalyse de la réaction type-Mannich que le complexe préparé in situ

Assessment of the Efficiency of Chemical and Thermochemical Depolymerization Methods for Lignin Valorization: Principal Component Analysis (PCA) Approach

Energy demand and the use of commodity consumer products, such as chemicals, plastics, and transportation fuels, are growing nowadays. These products, which are mainly derived from fossil resources and contribute to environmental pollution and CO2 emissions, will be used up eventually. Therefore, a renewable inexhaustible energy source is required. Plant biomass resources can be used as a suitable alternative source due to their green, clean attributes and low carbon emissions. Lignin is a class of complex aromatic polymers. It is highly abundant and a major constituent in the structural cell walls of all higher vascular land plants. Lignin can be used as an alternative source for fine chemicals and raw material for biofuel production. There are many chemical processes that can be potentially utilized to increase the degradation rate of lignin into biofuels or value-added chemicals. In this study, two lignin degradation methods, CuO–NaOH oxidation and tetramethyl ammonium hydroxide (TMAH) thermochemolysis, will be addressed. Both methods showed a high capacity to produce a large molecular dataset, resulting in tedious and time-consuming data analysis. To overcome this issue, an unsupervised machine learning technique called principal component analysis (PCA) is implemented

Evaluation of the Adsorption Efficiency of Graphene Oxide Hydrogels in Wastewater Dye Removal: Application of Principal Component Analysis

Industrial dye wastewater is one of the major water pollution problems. Adsorbent materials are promising strategies for the removal of water dye contaminants. Herein, we provide a statistical and artificial intelligence study to evaluate the adsorption efficiency of graphene oxide-based hydrogels in wastewater dye removal by applying Principal Component Analysis (PCA). This study aims to assess the adsorption quality of 35 different hydrogels. We adopted different approaches and showed the pros and cons of each one of them. PCA showed that alginate graphene oxide-based hydrogel (without polyvinyl alcohol) had better tolerance in a basic medium and provided higher adsorption capacity. Polyvinyl alcohol sulfonated graphene oxide-based hydrogels are suitable when higher adsorbent doses are required. In conclusion, PCA represents a robust way to delineate factors affecting hydrogel selection for pollutant removal from aqueous solutions

The Application of Principal Component Analysis (PCA) for the Optimization of the Conditions of Fabrication of Electrospun Nanofibrous Membrane for Desalination and Ion Removal

Nowadays, acquiring a water supply for urban and industrial uses is one of the greatest challenges facing humanity for ensuring sustainability. Membrane technology has been considered cost-effective, encompasses lower energy requirements, and at the same time, offers acceptable performance. Electrospun nanofibrous membranes (ENMs) are considered a novel and promising strategy for the production of membranes that could be applied in several treatment processes, especially desalination and ion removal. In this study, we apply an unsupervised machine-learning strategy, the so-called principal component analysis (PCA), for the purpose of seeking discrepancies and similarities between different ENMs. The main purpose was to investigate the influence of membrane fabrication conditions, characteristics, and process conditions in order to seek the relevance of the application of different electrospun nanofibrous membranes (ENMs). Membranes were majorly classified into single polymers/layers, from one side, and dual multiple layer ENMs, from another side. For both classes, variables related to membrane fabrication conditions were not separated from membrane characterization variables. This reveals that membranes’ characteristics not only depend on the chemical composition, but also on the fabrication conditions. On the other hand, the process conditions of ENM fabrication showed an extensive effect on membranes’ performance

( R )‐BINOL‐6,6’‐bistriflone: Shortened Synthesis, Characterization, and Enantioselective Catalytic Applications

International audienceThe title compound, characterized by X-ray crystallography, was accessed in 4 steps with 92 % ee. and 25 % yield from an O-protected (R)-BINOL precursor. This revised synthetic route relied on a chlorosulfonylation reaction, as a shortcut to a previously developed sequence requiring the use of toxic SO2 gas and bromine. The strongly electron-impoverished (R)-6,6′-Tf2-BINOL proved an effective ligand in metal-catalyzed enantioselective transformations such as a Zr-based Mannich-type reaction. The catalytic species was characterized by X-ray crystallography as a unique tetrameric metal cluster. The 6,6′-bistriflone groups also allowed to exalt the H-bond donor capacity of the BINOL moiety, as illustrated in an organocatalyzed Morita-Baylis-Hillman transformation. Theoretical study indicated that the 6,6′-bistriflone groups induce a drop of the phenol acidity of 5 pKa units in DMSO. Overall, this work simplified the access, completed the characterization, and confirmed the potential of (R)-6,6′-Tf2-BINOL as a promising platform to further elaborate activated chiral metal ligands or organocatalysts

Towards Understanding Aerogels’ Efficiency for Oil Removal—A Principal Component Analysis Approach

In this study, our aim was to estimate the adsorption potential of three families of aerogels: nanocellulose (NC), chitosan (CS), and graphene (G) oxide-based aerogels. The emphasized efficiency to seek here concerns oil and organic contaminant removal. In order to achieve this goal, principal component analysis (PCA) was used as a data mining tool. PCA showed hidden patterns that were not possible to seek by the bi-dimensional conventional perspective. In fact, higher total variance was scored in this study compared with previous findings (an increase of nearly 15%). Different approaches and data pre-treatments have provided different findings for PCA. When the whole dataset was taken into consideration, PCA was able to reveal the discrepancy between nanocellulose-based aerogel from one part and chitosan-based and graphene-based aerogels from another part. In order to overcome the bias yielded by the outliers and to probably increase the degree of representativeness, a separation of individuals was adopted. This approach allowed an increase in the total variance of the PCA approach from 64.02% (for the whole dataset) to 69.42% (outliers excluded dataset) and 79.82% (outliers only dataset). This reveals the effectiveness of the followed approach and the high bias yielded from the outliers