Resorcinarenes for intra-cavity catalysis – RESICAT

Homogeneous catalysts operating in cavities or containers exclusively made of covalent bonds have not been reported to date. The aim of this proposal is to used the resorcin[4]arenes as a preorganisation platform and to graft one or two phosphorus atoms or an imidazol group. The formed cavitands should be able to host a catalytic center.

The realized work has allowed to synthesize and to study cavitands grafted with one phosphine or imidazolium moiety respectively. These ligands were evaluated in carbon-carbon bond forming reactions. It was also possible to confine the metal center in a capsule or a cavitand bearing two iminophosphorane two functions. With the latter ligand, substrate discrimination was observed for the hydrogenation of a-olefins.


Since the beginning of this project, we were able to synthesise and to study two families of cavitands bearing a phosphine or an imidazolium unit, respectively. These ligands were tested in Suzuki-Miyaura and Kumada-Tamao-Corriu cross-coupling reactions.

We performed the synthesis of novel ligands. Their use in homogeneous catalysis is still in progress, particularly for metallo-capsules in which, the metal containment should strongly influence the regioselectivities of the catalytic reactions. Recycling of the catalyst (catalysis in water and immobilization of the complexes in polymer) remains under consideration.

The published results deal with the synthesis of imidazolium salts grafted on a resorcin[4]arene platform and their application in cross coupling reactions (Eur. J. Org. Chem., 2013, 4443 and Turk. J. Chem. in press ) and the use of resorcinarenyl mono-phosphines in Suzuki-Miyaura coupling of aryl chlorides (Eur. J. Inorg. Chem., 2014, 1364). Atempts to coordination the latter phsophine with cations allowed us to observe the regioselective breaking of a methylene bridge adjacent to the phosphorus atom and the formation of P,O-chelate complexes (Chem. Eur. J., 2015, 21 , 6678).

Capitalising on our experience in the field of constrained ligands based on a macrocyclic scaffold, we propose a three-year program aimed at producing catalytic reactions taking place inside a molecular cavity. Homogeneous catalysts operating in cavities or containers exclusively made of covalent bonds have not been reported to date. This project involves the use of a specific class of macrocycles, namely resorcin[4]arenes, which are receptors that can be chemically modified and made rigid so as to delineate large cavities suited for the construction of confined molecular catalysts. Three types of ligands will be considered, all having trivalent phosphorus atoms connected to the larger rim of a conical resorcinarene backbone: monophosphanes, diphosphanes and diiminophosphoranes. The presence of a cavity able to host a catalytic centre is mainly expected to favour substrate discrimination. On the other hand the presence of a rigid ligand backbone should introduce strain in the targetted ligands and therefore result in increased regioselectivities. Complexes of the ligands will be assessed in carbon-carbon bond forming reactions such as Suzuki-Miyaura, olefin polymerisation, allylic substitution, and olefin hydroformylation. Recycling of the catalysts, which constitutes an important issue in contemporary chemistry, will be also studied, notably by preparing polymeric derivatives. An alternative will consist in making the resorcinarene derivatives soluble in water or ionic liquids. The present research is a fundamental contribution to the discovery of homogeneous catalysts operating in a confined environment.