Micro-ondes et activation mécanique (applications en synthèse organique et peptidique)

La chimie verte ou chimie pour le développement durable est un domaine en pleine expansion depuis quelques années. La nécessité de limiter l'impact des activités humaines sur l'environnement et la santé, de trouver de nouvelles ressources pour les réactifs et les solvants nous oblige à envisager une nouvelle manière de faire de la chimie. Parmi tous les domaines de la chimie verte, nous avons choisi de travailler sur le développement de nouvelles méthodes permettant d'effectuer des réactions en conditions sans solvant. Parmi ces méthodes, nos travaux se sont particulièrement portés sur les micro-ondes et l'activation mécanique. Nous avons ainsi développé une méthode sans solvant pour la réaction de Pétasis, permettant de préparer une large variété de tricycles en une seule étape et avec un lavage basique pour seule purification. Nous avons aussi montré qu'il était possible de réaliser un couplage de Suzuki en 10 min à 110C sans utiliser de support solide tel que l'alumine et avec un nouveau catalyseur, le PEPPSI. Utilisant l'activation mécanique, nous avons montré tout l'intérêt de cette méthode pour la préparation de nitrones et d'hydrazones, composés obtenus après condensation d'une amine sur un carbonyle. Les hydrazones ont aussi pu être N-alkylées en conditions basiques. Nous avons aussi montré l'applicabilité de l'activation mécanique dans la synthèse de di et tripeptides en utilisant des aminoacides activés sous forme d'Uréthane N-carboxyanhydrides (UNCA). Les peptides sont obtenus par simple broyage en conditions basiques d'un UNCA avec un chlorhydrate d'aminoester. Enfin nous avons réalisé l'un des premiers exemples d'application en synthèse asymétrique de broyage sans solvant pour l'alkylation de bases de Schiff en présence de sels de cinchonidine, permettant d'obtenir des aminoacidesGreen or Sustainable chemistry has become a growing area in the last few years. The necessity to limit the impact of human activities on environment and health, to find new resources for reactants and solvents drives us to develop a new way to perform chemistry. For this purpose, we have chosen to work on the development of new methods allowing us to perform solvent-free reactions. Among all these methods, mechanical and microwaves activations were specifically studied. Using microwaves, we first developed solvent-free Petasis reactions, giving a large variety of tricycles in one step and with a basic aqueous wash as the only purification step. We also showed that the Suzuki coupling could be performed in 10 min at 110C without any solid support such as alumina and using a new NHC-Pd catalyst, the PEPPSI. Using mechanical activation, the interest of this method for the synthesis of nitrones and hydrazones was proven, the compounds were obtained after condensation of an amine on a carbonyle. Hydrazones could also be N-alkylated in a second step in basic conditions. The applicability of mechanical activation to prepare di- and tri-peptides using activated aminoacids, Urethane N-carboxyanhydrides (UNCA), was also shown. Peptides were obtained after ball-milling a UNCA with an aminoester chlorhydrate in basic conditions. Finally, one of the first applications of a ball-mill in asymmetric synthesis was realized, in order to prepare aminoacids after alkylation of Schiff bases in presence of cinchonidinium saltsMONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Microwave-Assisted Neat Procedure for the Petasis Reaction

International audienceA new solvent-free microwave-assisted procedure for the Petasis multicomponent reaction was developed. This method is the first application of the borono-Mannich reaction in solvent-free conditions and proved its applicability to various boronic acids and secondary amines. Results are very good in term of yields, with shorter reaction time than with classic methods. Because of the efficiency of the method, full conversion of the starting materials towards the expected product was achieved, starting from stoichiometric quantities of reactants, avoiding the usual solvent consuming column chromatography on silica gel. No other purification step than an aqueous washing was required

Solvent-Free Microwave-Assisted Suzuki-Miyaura Coupling Catalyzed by PEPPSI-IPr

International audienceWe have developed a new method for Suzuki coupling using an NHC-stabilized palladium catalyst under solvent-free conditions using microwave activatio

Synthesis Short Review Visible-Light Driven Transformations of Phenols via Energy Transfer Catalysis

International audienceIn the past decade, the field of visible-light mediated photocatalysis has been particularly thriving by offering innovative synthetic tools for the construction of functionalized architectures from simple and readily available substrates. One strategy that has been of interest is energy transfer catalysis which a powerful way of activating a substrate or an intermediate by using the combination of light and a relevant photosensitizer. This review deals with recent advances in energy transfer catalysis applied to phenols which are ubiquitous in chemistry both as starting materials and as high-added value products. Processes involving energy transfer from the excited photosensitizer to ground state oxygen and to phenol-containing substrates will be described

Solvent-Free Synthesis of Peptides

International audienceA crush on sweetness ! A novel solvent-free methodology for the synthesis of peptides was developed: the coupling of an urethane protected N-carboxy anhydride (UNCA) of an aminoacid with another aminoacid derivative gave a protected dipeptide in very high yield under ball-milling conditions. The reaction is taking place in the solid state. This solvent-free synthesis was applied to the preparation of dipeptides and tripeptides, and exemplified in the preparation of Aspartame, in three steps, using the UNCA route, without any organic solvent and purification

aza -Baylis−Hillman Reaction

International audienc

One-Pot Synthesis of Functionalized Fused Furans via a BODIPY-Catalyzed Domino Photooxygenation

Six-membered ring fused furans containing a tetrasubstituted tertiary carbon were prepared in an unprecedented one-pot BODIPY-catalyzed domino photooxygenation/reduction process. A series of functionalized furans was synthesized from readily available 2-alkenylphenols and mechanistic studies were performed to account for the domino photosensitized oxygenation