Jonathan Potier

Cyclodextrin-grafted polymers functionalized with phosphanes: a new tool for aqueous organometallic catalysis

Summary New cyclodextrin (CD)-grafted polymers functionalized with water-soluble phosphanes were synthesized in three steps starting from polyNAS. Once characterized by NMR spectroscopy and size-exclusion chromatography, they were used as additives in Rh-catalyzed hydroformylation of 1-hexadecene. The combined supramolecular and coordinating properties of these polymers allowed increasing the catalytic activity of the reaction without affecting the selectivities.

A Simple and Efficient Protocol for the Catalytic Insertion Polymerization of Functional Norbornenes

Norbornene can be polymerized by a variety of mechanisms, including insertion polymerization whereby the double bond is polymerized and the bicyclic nature of the monomer is conserved. The resulting polymer, polynorbornene, has a very high glass transition temperature, Tg, and interesting optical and electrical properties. However, the polymerization of functional norbornenes by this mechanism is complicated by the fact that the endo substituted norbornene monomer has, in general, a very low reactivity. Furthermore, the separation of the endo substituted monomer from the exo monomer is a tedious task. Here, we present a simple protocol for the polymerization of substituted norbornenes (endo:exo ca. 80:20) bearing either a carboxylic acid or a pendant double bond. The process does not require that both isomers be separated, and proceeds with low catalyst loadings (0.01 to 0.02 mol%). The polymer bearing pendant double bonds can be further transformed in high yield, to afford a polymer bearing pendant epoxy groups. These simple procedures can be applied to prepare polynorbornenes with a variety of functional groups, such as esters, alcohols, imides, double bonds, carboxylic acids, bromo-alkyls, aldehydes and anhydrides.

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.

Pillar[5]arenes as supramolecular hosts in aqueous biphasic rhodium-catalyzed hydroformylation of long alkyl-chain alkenes

Aqueous biphasic catalysis continues to attract strong interest, especially when very hydrophobic substrates are concerned. Indeed, their insolubility in water strongly limit their transformation by water‐soluble organometallic catalysts. To improve contacts between the substrate‐containing organic phase and the catalyst‐containing phase, one of the best solutions consists in using interfacial additives capable of supramolecularly recognize the substrate and/or the catalyst. In the present study, modified pillar5arenes are considered as interfacial additives and their performance is assessed in Rh‐catalyzed hydroformylation of long alkyl‐chain alkenes (higher olefins). Pillar5arenes substituted by carboxylate functions and methyl groups P5 A‐(Me)10‐x‐(CH2COOMe)x are compared to pillar5arenes substituted by polyethylene glycol (PEG) chains (P5 A‐(Me)5‐(PEG)5 and P5 A‐(PEG)10). Utilization of P5 A‐(Me)10‐x‐(CH2COOMe)x leads to high conversion and regioselectivity (linear/branched aldehyde ratio) in Rh‐catalyzed hydroformylation of 1‐decene and 1‐hexadecene. Compared with other interfacial additives such as modified cyclodextrins, the studied pillar5arenes show lower chemo‐selectivity, similar catalytic activity and higher regioselectivity.