Un fil twitter qui regroupe les publications reliées à l'iode hypervalent de plus de 100 journaux.
A twitter feed that aggregates the publications about hypervalent iodine from over 100 journals.
Prof. Claude Y. Legault
Université de Sherbrooke
Département de Chimie
2500 boul. de l'Université, D1-3029
Sherbrooke (QC) J1K 2R1
Programme de visualisation et d'analyse
Visualization and analysis program
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The chemical industry is facing an increasing number of challenges. For example, the emergence of drug-resistant pathogens requires the development of new antibiotic drugs to protect vulnerable populations. Furthermore, with a constant increase in drug consumption in the aging population, the development of fabrication processes with lesser environmental impact is of the utmost importance. In this context, organic synthesis plays a vital role. Indeed, the development of new synthetic methods for the creation and evaluation of new molecules of biological interest is the foundation on which we improve the drugs available to treat illnesses. It can also serve to improve the manufacturing processes of known drugs and reduce their environmental footprint.
Our research program focuses on the development of new synthetic methodologies with the aim of improving the access to compounds with high-value to the industry. Our group has a unique expertise in both experimental and computational organic/organometallic chemistries. Consequently, we rely on joint experimental/computational studies to accelerate the research process and enhance our understanding of the studied reactions. Our group focuses on three main areas of research: 1) Iodine(III)-mediated Chemistry; 2) Organometallic Catalysis; 3) Applied Computational Chemistry.
Oxidative transformations are key synthetic methods as they enable rapid increase in molecular complexity. For this reason, tremendous efforts have been put forward to improve this class of useful processes. The development of hypervalent iodine reagents and their application in synthesis have been of particular interest in this regard. They tend to be eco-friendly, being carbon-based and usually biodegradable, and have been found to be in numerous cases a good alternative to toxic heavy metal-based reagents. In particular, iodine(III) reagents have served in a diverse array of synthetic methodologies, such as phenolic dearomatization chemistry, which has enabled access to certain complex molecular structures much more rapidly.
Axis 1b - Development of new iodine(III) reagents: A crucial part of the development of new iodine(III)-mediated reactions is the investigation of new types of hypervalent iodine compounds. In 2012, during the investigation of iodine(III)-mediated halogenation reactions, we reported the synthesis of a new fluoroiodane (A), which has been used by numerous groups in the past 6 years. More recently, we are investigating the properties and synthetic applications of a new family of iodonium zwitterions (B).
Axis 1c - Investigation of the properties and mechanisms of iodine(III) reagents: The development of better methodologies comes from a better understanding of the reagents involved in the processes. Using our unique expertise in computational chemistry, we have been investigating different iodine(III)-mediated reactions in the past years, such as the metathetical redox reaction of (diacetoxyiodo)arenes and Iodoarenes, and the α-tosyloxylation of ketones. More recently, we have been working on the quantification of the Lewis acidity of iodonium species.
Axis 1a - Synthesis of α-substituted ketones: We have worked since 2009 on the development of iodine(III)-mediated reactions to access chiral nonracemic α-substituted ketones. The development of practical methods to access these chiral building blocks is of particular importance due to the ubiquitous nature of these products. We have investigated numerous strategies in this area: the directed α-tosyloxylation of ketones, the oxidation of enol esters, as well as the oxidative hydrolysis of haloalkenes. This work is summarized in this account.
This field has revolutionized synthetic chemistry in the last 50 years. The diversity of accessible reactions makes it a tool of choice. To create an efficient catalyst, a balance between its stability and reactivity must be attained. These properties are controlled not only by the transition metal used, but also by the ligands on the complex. The synthesis of new types of ligands thus enable the creation of catalysts having new properties. We are particularly interested in the development of anionic carbene (NHC) ligands. Initially reported by Charette and co-workers, we are developing new families based on N-iminoimidazolium ylides. We have investigated and reported in 2013 an extended variant based on the acyl anionic tether. We have recently reported a new ligand family based on a sulfonyl anionic tether. We are currently developing synthetic methods using catalysts derived from these ligands.
Applied Computational Chemistry
A key tool in our research program is computational chemistry. It is through the theoretical study of reaction mechanisms that synergy arises between the experimental and computational fields. Since 2010, we have also shared our expertise with numerous groups:
(4+1)-cycloaddition reaction of electron-rich carbenes – Claude Spino (UdeS): The selectivity behaviour of highly reactive carbene intermediates was studied. Computational chemistry was instrumental for this study and shows the potential of using this tool in synergy with experiments.
SN2 reaction of organofluorides – Jean-François Paquin (Université Laval): We shed light on an acceleration effect in a reaction of synthetic interest. Computational chemistry was not only a tool but an important contribution to this publication to rationalize the chemical behaviour observed.
Origins of reactivity in Copper-catalyzed O-arylation of aminoalcohols – Alexandre Gagnon (UQAM): We provided a way to rationalize a particular reactivity pattern.
Origin of Chemoselectivity in NHC-catalyzed cross-benzoin reactions – Michel Gravel (University of Saskatchewan): This publication was largely based on computational results to rationalize the observed chemoselectivity in a previously published reaction.
Origin of selectivity in the synthesis of fluorinated iminosugars – Olivier Martin (Université d’Orléans): We provided a rational to explain the stereochemical aspects of this synthetic method.
Selectivity of the Minisci reaction on cyclopropanol derivativeds – Arturo Orellana (York University): We calculated the ionization potentials of the studied substrates in order to evaluate if a trend existed between this property and their reactivity.
Software Development : CYLview
The efficient analysis and communication of scientific results are a vital portion of the work of any chemist. This aspect is even more important for computational chemists, due to the amount and complexity of computational results. The present major challenge with the preparation of publication quality representations of structures is the need to use multiple programs to achieve the desired result. In this regard, I created CYLview to accelerate the evaluation and analysis of computed structures, as well as to generate in the same program high quality representations, containing all the information (e.g. bond distances, angles, atom numbering) needed for professional publications and presentations. It is currently used by over 3000 computational chemists around the world and was cited in more than 850 publications since 2009.