Catalysis in Cyclodextrin-Based Unconventional Reaction Media

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Catalysis in Cyclodextrin-Based Unconventional Reaction Media: Recent Developments and Future Opportunities Frédéric Hapiot, Stéphane Menuel, Michel Ferreira, Bastien Léger, Hervé Bricout, Sébastien Tilloy, and Eric Monflier* Unité de Catalyse et de Chimie du Solide (UCCS), Faculté des Sciences Jean Perrin, University of Artois, CNRS, Centrale Lille, ENSCL, University of Lille, UMR 8181, rue Jean Souvraz, SP18, F-62300 Lens, France ABSTRACT: During these last years, cyclodextrins (CDs) have greatly contributed to the development of innovative homogeneous or heterogeneous catalytic processes. More than simple molecular platforms aiming at designing new ligands or interfacial additives, CDs have been employed to generate unconventional reaction media such as supramolecular hydrogels or low melting mixtures (LMMs) capable of stabilizing active catalytic species. By using such alternative and unconventional media, high catalytic activities and selectivities were obtained in various transition metal catalytic reactions. The studied catalytic systems are easy to implement and allow for the remarkable stabilization of organometallic or metal nanoparticle catalysts. Interestingly, the size of metal nanoparticles can be finely tuned through confinement in the network of CD-based supramolecular hydrogels. Additionally, the catalysts can be recovered by a simple phase separation. The catalytic phase can be stored at room temperature under an air atmosphere in the solid state and reused as needed without significant loss of activity. Eventually, such CD-based catalytic systems greatly improve process safety. The present article intends to show the reader the very substantial progress that has recently been made in the field. KEYWORDS: Catalysis, Supramolecular assembly, Hydrogel, Low melting mixtures, Thermoresponsive systems

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(RCH/RP process).1,2 The products being insoluble in water, they can be easily recovered by simple decantation. Extension of this process to hydrophobic substrates were developed using the tools of supramolecular chemistry.3−5 The opposite approach has also been studied for water-soluble substrates.6 Other strategies rely on (i) the immiscibility of organic polar and nonpolar organic liquids (SHOP process),7 supercritical CO2,8−10 (iii) ionic liquids having a low melting point,11−13 (iv) fluorous biphasic catalysis,14 and (v) multiphasic heterogeneous catalysis mediated by catalystphilic liquid phases.15 Recently, approaches have been developed which make use of organic solvent nanofiltration,16 amphiphilic nanogels,17 continuous liquid−vapor reactors,18,19 temperature dependent water surfactant systems,20−22 or aqueous thermomorphic multicomponent solvent systems.23,24 Herein we report on the recent advances in the field using thermoresponsive cyclodextrin based hydrogels or low-melting mixtures (LMMs) as catalyst-containing phase. The purpose of

INTRODUCTION Although the roots of catalysis can be traced as far back as the 18th century, a great deal of research activity is still being devoted to the elaboration of catalysts. This enthusiasm mainly lies in the urgent need for the development of eco-friendly chemical processes. Currently, 90% of all commercial chemicals are synthesized from catalyzed reactions. However, efforts should still be made to improve the catalytic performances. In this context, transition metal catalysis is one of the best approach as the catalytic activity and selectivity can be finely tuned by a judicious choice of first- and/or second-sphere ligands. Countless strategies have thus been developed using organometallic catalysts for the synthesis of a wide range of organic substrates. However, from a sustainable chemistry viewpoint, few synthetic processes truly meet the requirements of sustainable chemistry in terms of reduction of cost and energy consumption. In this context, recovery and reuse of the catalyst is mandatory for the chemical process to be economically viable at the industrial scale. As such, homogeneous organometallic catalysis in organic solvent is not an adequate solution as the products and the catalyst are soluble in the same phase once the reaction is complete. Accordingly, alternative solutions have emerged to separate the products and the catalyst. The most famous one employs water as a catalyst-dissolving solvent for the biphasic hydroformylation of lower olefins partially soluble in water © 2017 American Chemical Society

Special Issue: Asia-Pacific Congress on Catalysis: Advances in Catalysis for Sustainable Development Received: November 29, 2016 Revised: January 4, 2017 Published: January 18, 2017 3598

DOI: 10.1021/acssuschemeng.6b02886 ACS Sustainable Chem. Eng. 2017, 5, 3598−3606

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ACS Sustainable Chemistry & Engineering

becomes saturated with α-CD/PEO crystallites over time and the catalytic activity levels off. Such saturation phenomenon had already been described in the literature.42,43 This interfacial saturation is easily overcome by successive depressurization− pressurization sequences and heat and cool cycles. That way, dynamics of exchange are recovered at the aqueous/organic interface and full conversion of C10−C18 alkenes is reached through this step-by-step procedure. While the chemoselectivity is improved compared to aqueous solution of CDs, the regioselectivity remains rather constant (linear/branched aldehydes ratio in the 2.3−2.9 range), suggesting that the equilibriums existing between the rhodium catalytic species within the hydrogel network are not significantly modified. The efficacy of the previous hydrogel-based system is greatly improved when randomly methylated β-CD (RAME-β-CD) or randomly methylated γ-CD (RAME-γ-CD) is added to the α-CD/PEO mixture in a controlled quantity.44 In that case, the reaction proceeds with a very short reaction time in one go. For example, 1-dodecene and 1-hexadecene are fully converted using a hydrogel/RAME-β-CD combination within only 1 and 1.5 h, respectively, following an almost linear conversion variation. The TOF values are the highest ever obtained for such hydrophobic substrates under aqueous biphasic conditions (140 h−1 for 1-dodecene and 93 h−1 for 1-hexadecene). Even biobased substrates such as methyl 10-undecenoate undergoes a total conversion within 1 h, and 25% of the more challenging CC bond of methyl oleate is still hydroformylated. Actually, compared to the separated components, the combination of the Pickering emulsion and RAME-β-CD or RAME-γ-CD results in a synergetic effect. RAME-β-CD or RAME-γ-CD acts as fluidifier of the aqueous/organic interface and prevent the saturation of the oil droplet by the α-CD/PEO crystallites. Additionally, RAME-β-CD also recognizes higher olefins (hydrophobic effect) and participated in their conversion by supramolecular means (Figure 2). The chemoselectivity is also positively affected. For example, in hydroformylation of 1-hexadecene, the proportion of aldehydes increased to 77% in the presence of RAME-β-CD (vs 64% without RAME-β-CD), probably because of the well-known protecting ability of the CD cavity toward the terminal CC bond (limitation of side isomerization reactions).45 Note that the Rh-catalyst embedded into the supramolecular hydrogel network could be efficiently recycled without loss neither in catalytic activity nor selectivites (Figure 3). Thus, not only do CDs act as constitutive building blocks of the hydrogels, but they also participate in the olefin conversion as molecular receptor, supramolecular host and fluidifier of the aqueous/organic interface. To take the idea a step further, the multifunctional role of CDs has been extended to hydrogels consisting of conventional sequential and reverse-sequential poloxamines (also known as Tetronics macromolecules).46 These block copolymers have a X-shaped structure consisting of hydrophilic poly(ethylene oxide) (PEO) and hydrophobic poly(propylene oxide) (PPO) attached to an ethylene diamine spacer (Figure 4). In this study were considered the conventional sequential Tetronics701 (Mw 3600, 2.1 EO and 14 PO units per arm) and the reversesequential Tetronic90R4 (Mw 7200, 16 EO and 18 PO units per arm). Combinations of Tetronics and α-CDs form hydrogels through noncovalent interactions in a well-defined concentration range.47,48 As described previously, CDs selectively accommodate the PEO blocks and form stacked nanocylinders that aggregate into nanosized columnar α-CD domains. Below 25 °C,

this article is to put into perspective the utilization of these novel media in transition metal catalysis. Comments will be made on the compared catalytic activity of each catalytic system. The specific properties of thermoresponsive cyclodextrin (CD) based supramolecular hydrogels and LMMs over other catalytic systems will be especially highlighted.

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RESULTS AND DISCUSSION Catalysis and Supramolecular Hydrogels. Hydrogels are soft materials generated by the entrapment of large quantities of water within a reticulated superstructure made of fibrils of varying dimensions. Due to their porous and hydrated molecular structure, they have especially been used in biology and medicine.25,26 Hydrogels can be of chemical or physical nature, polymeric or generated by low molecular weight gelator molecules. While chemical hydrogels are 3D networks consisting of covalently bonded components, physical hydrogels are formed through noncovalent interactions such as hydrogen bonding, hydrophobic interaction, metal−ligand coordination, van der Waals forces, and micro- or nanocrystallite formation. Such supramolecular hydrogels currently find applications in biology,27−29 sensing,30−32 and materials.33−35 Their threedimensional cross-linked macromolecular networks also found application in catalysis.36 In the gel phase, the solid-like structure confine reactants in an organized environment and make them react selectively.37−39 A hydrogel-based system capable of continuous self-monitoring and self-regulating behavior also yields very interesting results in four exothermic catalytic reactions.40 One of the main interest of supramolecular hydrogels lies in their dynamic nature. Indeed, physical hydrogels often exhibit reversible sol−gel transition upon exposure to external stimuli such as temperature. Such physicochemical property has been exploited in transition metal catalysis, especially to recover and recycle the organometallic catalyst. Supramolecular hydrogels consisting of poly(ethylene oxide) (PEO) and α-cyclodextrin (α-CD) contain nanosized columnar α-CD domains (nanocrystallites) which, under catalytic conditions, form Pickering-like emulsions that are particle-stabilized emulsions.41 Pickering-like emulsions act as emulsifiers and favor molecular contacts between substrates and catalysts. In aqueous Rh-catalyzed hydroformylation of higher olefins, saturated solutions of native α-CD and PEO (PEO20000 or PEO35000) prove effective to form Pickering-like emulsions, the crystallites being located at the water/oil interface (Figure 1).

Figure 1. Pickering-like emulsions consisting of alkene droplets partially covered with α-CD/PEO crystallites (see the zoomed area) and a catalyst-containing sol phase.

For example, at 80 °C under 50 bar of CO/H2 using Rh(CO)2(acac) as a rhodium precursor and TPPTS as a watersoluble ligand (Rh/TPPTS/substrate = 1:5:140), 80% of 1-decene is converted into its corresponding linear and branched aldehydes over 3 h (TOF = 37 h−1). However, the aqueous/organic interface 3599


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Figure 2. Synergetic effect of α-CD-based Pickering-like emulsions and RAME-β-CD in Rh-catalyzed hydroformylation of higher olefins.

room temperature once the reaction is complete, both the product and the Rh-catalyst are recovered in two different phases. Tetronic90R4-based catalytic systems give higher conversions than those obtained with α-CD/PEO combinations and slightly lower conversions than those obtained with hydrogel-based systems consisting of α-CD, PEO, and RAME-β-CD (as fluidifier) under the same catalytic conditions. For example, the TOF values obtained in hydroformylation of 1-dodecene at 80 °C under 50 bar of CO/H2 (1:1 stoichiometry) in α-CD/PEO, α-CD/PEO + RAME-β-CD, and α-CD/Tetronic90R4 are 28, 136, and 125 h−1, respectively. Although the α-CD/Tetronic90R4 system is slightly less effective than the α-CD/PEO + RAME-β-CD system, its main advantage lies in the all-in-one texture. No fluidifier is needed as Tetronic90R4 contain the interfacial properties required to “fluidize” the aqueous/organic interface. Moreover, the aldehyde selectivity and the linear to branched aldehyde ratio remain constant over the course of the reaction, suggesting that the equilibria between the Rh-species are not perturbed under such catalytic conditions. The reaction can be carried out at pressure of CO/H2 (1:1 stoichiometry) as low as 10 bar without significantly affecting the catalytic performances. This clearly indicates that the diffusion of CO and H2 is not the limiting step of the reaction rate. The scope of the α-CD/Tetronic90R4 hydrogels can be extended with success to the Rh-catalyzed hydroformylation of 1-octadecene with an appreciable TOF of 27 h−1 for such a hydrophobic substrate. Styrene and 2-vinylnaphthalene are also easily converted with 99% aldehyde selectivity. Such thermoresponsive hydrogels also ensure the reusability of the catalytic system. Indeed, excellent stability of the HRh(CO) (TPPTS)3 complex embedded into the Tetronic/ α-CD/water mixture is observed below and above the sol−gel transition temperature. Actually, the hydrogel prevents the oxidation of the Rh-coordinated phosphane resulting in unchanged catalytic performances upon recycling. The thermoresponsivity of supramolecular hydrogels was also applied to metal nanoparticle catalytic systems. For example, hydrogenation of alkenes can be carried out by using rutheniumnanoparticle (RuNPs) catalyst embedded into a supramolecular CD-based hydrogel matrix consisting of a mixture of the N-alkylpyridinium amphiphile [py-N-(CH 2 ) 12 OC 6 H 3-3,5(OMe)2]+ (Br−) (1) and α-CD.49 In water, 1 and α-CD selfassembled into the [3]pseudorotaxane 1·(α-CD)2 (Figure 5) and form a hydrogel network featuring a 42 °C sol−gel transition temperature.50 Reduction of RuCl3 by NaBH4 within the hydrogel leads to gel-embedded RuNPs, which is identified by the descriptor RuNPs@1·(α-CD)2. Interestingly, the hydrogel internal network structure exerts effective control over the RuNPs growth.

Figure 3. Recycling the Rh-catalyst embedded into the supramolecular α-CD/PEO hydrogel.

Figure 4. Structure of (a) conventional sequential poloxamines and (b) reverse-sequential poloxamines.

the system behaves as a gel while above 25 °C, it behaves as a liquid and forms a biphasic system. The gel-to-sol transition of Tetronic90R4/α-CD/water mixtures has been exploited in hydroformylation of higher olefins. Upon heating at 80 °C, the droplets of higher olefins are partially covered by the α-CD/ Tetronic90R4 polypseudorotaxane aggregates. The resulting Pickering-like emulsion favors contacts with the Rh-catalyst at the aqueous/organic interface. Upon cooling down the system to 3600


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hydrogels (prepared by copolymerization of N-isopropylacrylamide (NIPAAm) and 2-acrylamido-2-methyl 1-propansulfonic acid (AMPS)).52 AgNPs are obtained via reduction of AgNO3 by NaBH4. They form a narrow distribution within the hydrogel (1.6 wt %) with an average diameter centered at 3.5 nm. The lower critical solution temperature (LCST) of the resulting AgNPs@poly(NIPAAm-co-AMPS) hydrogels is 26 °C. Below the LCST, the system is in the hydrogel state while, around the LCST, the system shrink and expels the water molecules outside the 3D network. The catalytic properties of the system were assessed in the presence of α-CD at different temperatures in the reduction of 4-nitrophenol. Below the LCST, the slight increase in the reduction rate is attributed to the complexation between α-CD and 4-nitrophenol at the AgNPs surface. As expected, the magnitude of the increase of the reduction rate weakens as the temperature increases because of the lower association constant between α-CD and 4-nitrophenol. Above the LCST, the AgNP@ hydrogels shrink (Figure 7). Upon shrinkage, the molecular diffusion is then limited and the diffusion of the substrate greatly hampered. Such thermoresponsive systems could be used to control the reactivity of exothermic reactions. Similarly, thermoresponsive microgels were also used as unconventional medium for the synthesis of AuNPs. For example, copolymers consisting of poly(N-vinylcaprolactam) (PVCL) and α-CDs were successfully used to reduce HAuCl4 and stabilize the resulting AuNPs in situ without any additional surfactant and reducing agents.53 Both PVCL and CDs work as the

Figure 5. Thermoresponsive 1·(α-CD)2 supramolecular complex obtained by self-assembling of 1 and two α-CDs.

Their size (1.6 ± 0.33 nm) and shape are modulated by the volume of the hydrogel nanoregions (template effect). Upon heating, the gel phase turns into a sol phase and the association constant between α-CDs and 1 drops. “Free” CDs and 1 are then released within the sol phase to act as supramolecular carrier and surfactant, respectively, at the aqueous/organic interface (Figure 6). By combining the two effects, terminal and internal alkenes are efficiently hydrogenated under 40 bar of H2 with TOF values up to 350 h−1 (substrate/Ru = 100). The catalytic performance is far higher than any other catalytic activity obtained using CD-stabilized RuNPs in water for the hydrogenation of similar substrates (TOF up to 69 h−1).51 Here again, such supramolecular hydrogel allows for the reusability of the catalytic system. Upon cooling, the hydrogenated products and the RuNPs catalyst are recovered separately. The RuNPs@1·(α-CD)2 system can be recycled twice without any decline in activity. Another aspect of thermoresponsive CD-based hydrogels was recently highlighted. The catalytic system consists in CD-capped AgNPs immobilized in thermosensitive poly(NIPAAm-co-AMPS)

Figure 6. Thermoregulated RuNPs-catalyzed hydrogenation of alkenes in supramolecular hydrogel. 3601


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Figure 7. α-CD synergetic catalytic effect on AgNPs embedded in thermoresponsive p(NIPAAm-co-AMPS) hydrogels (Reproduced with permission from ref 52. Copyright 2016 Springer).

Figure 8. Schematic overview of the immobilization of 4-nitrophenol on the PVCL-α-CD-modified AuNPs surface within the microgel (Adapted with permission from ref 53. Copyright 2015 The Royal Society of Chemistry).

reducing agents.54 CD also act as stabilizer by chemisorption to the AuNPs surface through the hydroxyl groups.55 The AuNPs size can be controlled by the constrained environment of the microgel (template effect). Depending on the initial HAuCl4 concentration, AuNPs with diameter from 4.5 to 14.0 nm were obtained in the presence of PVCL-α-CD (13.08 wt %) microgels. The PVCL-α-CD-AuNPs microgel is used as a catalytic phase for the catalytic reduction of 4-nitrophenol and 2,6-dimethyl-4nitrophenol. Because of the complexation ability of α-CD with nitrophenol in aqueous solution,56 the local concentration of nitrophenol is increased near the AuNPs surface resulting in higher reduction rates compared to the reduction of 2,6-dimethyl-4nitrophenol whose bulky structure is not supramolecularly recognized by the α-CD cavity (Figure 8). Catalysis in Low-Melting Mixtures. Low-Melting Mixtures (LMMs) are fluid composed of two or three components, most of them being cheap, available in large amounts, biodegradable, biocompatible and nontoxic. These compounds are capable of self-association, often through hydrogen bond interactions. The mixture has a melting point lower than that of each individual component.57 Combinations of carbohydratesbased LMMs were used as eco-friendly solvents.58,59 For example, quantitative conversions were observed in carbon−carbon coupling reactions,60,61 copper-catalyzed azide alkyne 1,3-dipolar cycloaddition,62 or hydrogenation of methyl α-cinnamate.57

Recently, CD-based LMMs were also developed for applications in transition-metal catalysis. LMMs of N,N′-dimethylurea (DMU) and native or modified β-CD (weight ratio of 70/30) show a melting point around 90 °C while the melting point of DMU and β-CD are 104 and 270 °C, respectively.63 Mixtures obtained from native β-CD prove to be much more viscous (1165 Cp at 90 °C) than mixtures obtained from modified β-CDs (200−500 Cp at 90 °C). The relevance of DMU-CD LMMs as eco-friendly solvent was clearly established in Rh-catalyzed hydroformylation of 1-decene under 50 bar CO/H2 (1:1) at 90 °C using HRh(CO) (TPPTS)3 as a catalyst. The DMU/RAME-β-CD couple prove to be especially effective as 1-decene is fully converted within 1 h (TOF = 1980 h−1). The chemoselectivity is very high (95% aldehydes) and the regioselectivity is in line with hydroformylation carried out using TPPTS as a ligand in polar media (l/b = 2.4). These results indirectly substantiate the integrity of the catalytic system during the course of the reaction.64 The efficacy of the DMU/RAME-β-CD combination as solvents for transition metal catalysis was also assessed in a Tsuji−Trost reaction. Quantitative conversion of allyloctylcarbonate is observed in only 5 min at 90 °C under nitrogen with diethylamine as an allyl scavenger. The reaction proceeds very cleanly without any byproduct formation. Recycling experiments reveals the interest of such an approach. By cooling down the biphasic system to room temperature once the reaction is 3602



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CONCLUSION All the examples given above are a good illustration of the stimulating effect on innovative biphasic catalytic systems that can be achieved by exploration of unconventional aqueous phases such as hydrogels or LMM. Their main advantage relies on the easy implementation of the catalytic system. Indeed, the constitutive components of CD-based hydrogels or LMM are cheap and easy-to-handle basic components. Such soft materials can also protect ligands and organometallic catalysts against oxidation by reducing the diffusion of oxygen in the gel or solid phase. Accordingly, the catalyst can be recycled several times without significant decline in activity. The size of metal nanoparticles can also be finely controlled because of their confinement in the 3D structure of the CD-based supramolecular hydrogels. Eventually, by reducing the diffusion of the substrates within the reaction medium upon heating, some of the described catalytic systems are capable of self-controlling the exothermicity of the reaction and thus improve the safety process. The works described in this article provide compelling evidence that the knowledge is now at hand to design safe and easy-to-handle biphasic catalytic systems offering high performance and reusability. It is also likely that these new approaches will, in the next future, become a popular tool in the hands of chemists interested in catalysis and supramolecular interactions.

complete, the DMU-RAME-β-CD phase becomes solid and the organic layer is simply recovered under air-atmosphere without special precaution (Figure 9). Fresh substrate is then added to

Figure 9. Reaction media of Tsuji−Trost reaction at room temperature (left) and at 90 °C (right) (Reproduced with permission from ref 63. Copyright 2014 The Royal Society of Chemistry).

the DMU-RAME-β-CD phase and the resulting mixture is heated again at 90 °C under nitrogen. Following this recycling procedure, the catalytic system can be recycled 8 times without any loss of catalytic activity. Not only did DMU-RAME-β-CD LMM prevents the catalyst degradation, but its reusability is easy to implement. The study was then extended to other CDs, such as α-CD, γ-CD, hydroxypropyl, methylated, or acylated CDs.65 The DMU-CD melting points are weakly affected by the size and the chemical modification of the CD. Conversely, compared to native CDs, modified CDs lead to a decrease in viscosity of the LMMs. Assessed in Rh-catalyzed hydroformylation of 1-decene under the catalytic conditions described above, the DMU/RAME-β-CD combination (70/30) remains the best LMM. A comparison with the acyclic CD constitutive unit (α-D-methylglucopyranose) suggested that the hydroformylation process is not driven by the formation of inclusion complexes between the substrate and the CD. Interestingly, the conversion increases with the solubility of 1-decene and decreases with the LMM viscosity. Concurrently, a similar study was performed using lowmelting β-CD/N-methylurea (NMU) mixture as solvent in Suzuki and Heck couplings in the presence of fresh native β-CDcapped Pd0 nanoparticles (PdNPs).66 The catalytic system is ligand-free and can be implemented in air. β-CD-supported PdNPs are prepared by reduction of Na2PdCl4 with NaBH4 in DMF. Their size is in the 20−30 nm range, and the concentration is approximately 6 wt %. In β-CD/NMU mixture, they show high catalytic activity and give cross-coupled products in good to excellent isolated yields, especially in a Suzuki reaction carried out at 85 °C using K2CO3 as base and 0.05 mol % Pd. A catalytic amount of water is required probably to allow the substrate to reach the PdNPs surface (which is covered with β-CDs) and favor dynamics of exchange. Even challenging aryl chlorides give the corresponding products in moderate yields. Extended to the Heck reaction with iodobenzene and methyl acrylate as substrates and NEt3 as base, the β-CD-supported PdNPs/β-CD/ NMU catalytic system proves to be effective to convert aryl iodides but the catalytic performance significantly drops for aryl bromides. Contrary to the DMU-RAME-β-CD LMM catalytic system described previously, the recycling of the β-CD-supported PdNPs/β-CD/NMU catalytic system required addition of water and hexane. Moreover, PdNPs can only be recycled 4 times before aggregation phenomena lead to larger inactive PdNPs.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: eric.monfl[email protected]. ORCID

Frédéric Hapiot: 0000-0002-4394-8665 Michel Ferreira: 0000-0003-4898-0290 Eric Monflier: 0000-0001-5865-0979 Notes

The authors declare no competing financial interest. Biographies

Frédéric Hapiot received his Ph.D. from the University of Lille (France) in 1994 for his contribution to asymmetric catalysis research. He was promoted Associate Professor in 1995 at the University of Artois (France) where he studied liquid crystals and host−guest chemistry in the group of Eric Monflier. There, he completed his habilitation in 2006. In 2009, he moved to Florence (ICCOM, Italy) in the group of Maurizio Peruzzini. He became full Professor at the University of Artois in 2010. His current research is focused on design and characterization of supramolecular systems for molecular recognition, biphasic catalysis, and mechanochemistry. 3603


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Bastien Léger received his PhD Degree in 2007 from the University of Rennes 1 (France) for his research on the synthesis and the stabilization of metallic nanoparticles in nonaqueous ionic liquids and their application in the hydrogenation of olefinic and aromatic compounds. From October 2007 to August 2009, he joined the CASU Team of UCCS Artois Laboratory as a Research and Teaching Assistant and worked on the stabilization of metallic nanoparticles by supramolecular complexes in aqueous phase. Since 2009, he is an Assistant Professor in the CASU Team of UCCS Artois Laboratory. His current research interests focus on the stabilization of metallic nanoparticles in the presence of cyclodextrins in aqueous phase for different kind of catalytic applications especially for the conversion of biomass derived compounds. Stéphane Menuel joined the team “Supramolecular Catalysis” of UCCSArtois in 2007. He is recognized for its expertise in the synthesis of modified cyclodextrins and their applications in supramolecular chemistry and aqueous catalysis. His current research is focused on design and characterization of cyclodextrin-based supramolecular systems. He has played a key role in the development of supramolecular hydrogels capable of forming Pickering emulsions for the hydroformylation of very hydrophobic alkenes. His current work deals with supramolecular catalysis and mechanochemistry.

Hervé Bricout received his Ph.D. degree from the University of Lille I in 1997 under the supervision of Professor A. Mortreux. Then, he reached the research group headed by Professor E. Monflier and became assistant professor in 1997. His work deals with transition metal complexes modified by sulfonated phosphanes and soluble in water or in deep eutectic solvents. These metal complexes are used in biphasic catalysis in the presence of cyclodextrins as polyvalent promoters, mass transfer, and selectivity enhancement agents but also host molecules leading to specific catalytic species.

Michel Ferreira received his PhD degree in 2008 from the University of Artois (France) under the supervision of Prof. E. Monflier at the UCCS. He then spent one year as a postdoctoral fellow in the Supramolecular and Homogeneous Catalysis group of Prof. J. Reek at the University of Amsterdam in The Netherlands where he worked with Dr. Ir. J.I. van der Vlugt on the development of new catalysts for asymmetric hydroamination of biorenewable resources. In 2010, he became assistant professor in the University of Artois at the UCCS. His current research deals with the development of new homogeneous catalysts based on water-soluble ligands for biphasic processes using aqueous or deep eutectic solvents.

Sébastien Tilloy received his Ph.D. degree in 1998 from the University of Artois under the supervision of Professor Eric Monflier. In 2000, he became Associate Professor at the University of Artois where he completed his habilitation in 2004. In 2005, he moved to the University of Amsterdam (Netherlands) in the HomCat group headed by Professor Piet van Leeuwen and Professor Joost Reek. In 2006, he was promoted Full Professor. His research interests are centered on cyclodextrins and, more specifically, on their supramolecular implications in the field of organometallic catalysis in water or lowmelting mixtures. 3604


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(14) Horváth, I. T.; Rábai, J. Facile Catalyst Separation Without Water: Fluorous. Biphase Hydroformylation of Olefins. Science 1994, 266, 72− 75. (15) Tundo, P.; Perosa, A. Multiphasic heterogeneous catalysis mediated by catalyst-philic liquid Phases. Chem. Soc. Rev. 2007, 36, 532−550. (16) Dreimann, J. M.; Skiborowski, M.; Behr, A.; Vorholt, A. J. Recycling homogeneous catalysts simply via organic solvent nanofiltration: New ways to efficient catalysis. ChemCatChem 2016, 8, 3330. (17) Lobry, E.; Cardozo, A. F.; Barthe, L.; Blanco, J.-F.; Delmas, H.; Chen, S.; Gayet, F.; Zhang, X.; Lansalot, M.; D’Agosto, F.; Poli, R.; Manoury, E.; Julcour, C. Core phosphine-functionalized amphiphilic nanogels as catalytic nanoreactors for aqueous biphasic hydroformylation. J. Catal. 2016, 342, 164−172. (18) Bourne, S. L.; O’Brien, M.; Kasinathan, S.; Koos, P.; Tolstoy, P.; Hu, D. X.; Bates, R. W.; Martin, B.; Schenkel, B.; Ley, S. V. Flow Chemistry Syntheses of Styrenes, Unsymmetrical Stilbenes and Branched Aldehydes. ChemCatChem 2013, 5, 159−172. (19) Abrams, M. L.; Buser, J. Y.; Calvin, J. R.; Johnson, M. D.; Jones, B. R.; Lambertus, G.; Landis, C. R.; Martinelli, J. R.; May, S. A.; McFarland, A. D.; Stout, J. R. Continuous Liquid Vapor Reactions Part 2: Asymmetric Hydroformylation with Rhodium-Bisdiazaphos Catalysts in a Vertical Pipes-in-Series Reactor. Org. Process Res. Dev. 2016, 20, 901− 910. (20) Illner, M.; Müller, D.; Esche, E.; Pogrzeba, T.; Schmidt, M.; Schomäcker, R.; Wozny, G.; Repke, J.-U. Hydroformylation in Microemulsions: Proof of Concept in a Miniplant. Ind. Eng. Chem. Res. 2016, 55, 8616−8626. (21) Pogrzeba, T.; Müller, D.; Illner, M.; Schmidt, M.; Kasaka, Y.; Weber, A.; Wozny, G.; Schomäcker, R.; Schwarze, M. Superior catalyst recycling in surfactant based multiphase systems − Quo vadis catalyst complex? Chem. Eng. Process. 2016, 99, 155−166. (22) Schwarze, M.; Pogrzeba, T.; Seifert, K.; Hamerla, T.; Schomäcker, R. Recent developments in hydrogenation and hydroformylation in surfactant systems. Catal. Today 2015, 247, 55−63. (23) Rost, A.; Brunsch, Y.; Behr, A.; Schomäcker, R. Comparison of the activity of a rhodium-biphephos catalyst in thermomorphic solvent mixtures and microemulsions. Chem. Eng. Technol. 2014, 37, 1055− 1064. (24) Gaide, T.; Dreimann, J. M.; Behr, A.; Vorholt, A. J. Overcoming Phase-Transfer Limitations in the Conversion of Lipophilic Oleo Compounds in Aqueous Media−A Thermomorphic Approach. Angew. Chem., Int. Ed. 2016, 55, 2924−2928. (25) Peppas, N. A.; Hilt, J. Z.; Khademhosseini, A.; Langer, R. Hydrogels in Biology and Medicine: From Molecular Principles to Bionanotechnology. Adv. Mater. 2006, 18, 1345−1360. (26) Gaharwar, A. K.; Peppas, N. A.; Khademhosseini, A. Nanocomposite hydrogels for biomedical applications. Biotechnol. Bioeng. 2014, 111, 441−453. (27) Lee, K. Y.; Mooney, D. J. Hydrogels for tissue engineering. Chem. Rev. 2001, 101, 1869−1079. (28) Li, J.; Loh, X. Cyclodextrin-based supramolecular architectures: syntheses, structures, and applications for drug and gene delivery. Adv. Drug Delivery Rev. 2008, 60, 1000−1017. (29) Rodríguez-Llansola, F.; Miravet, J. F.; Escuder, B. Aldehyde responsive supramolecular hydrogels: towards biomarker-specific delivery systems. Chem. Commun. 2011, 47, 4706−4708. (30) Fenzl, C.; Wilhelm, S.; Hirsch, T.; Wolfbeis, O. S. Optical sensing of the ionic strength using photonic crystals in a hydrogel matrix. ACS Appl. Mater. Interfaces 2013, 5, 173−178. (31) Zhang, C.; Liu, C.; Xue, X.; Zhang, X.; Huo, S.; Jiang, Y.; Chen, W.-Q.; Zou, G.; Liang, X.-J. Salt-responsive self-assembly of luminescent hydrogel with intrinsic gelation-enhanced emission. ACS Appl. Mater. Interfaces 2014, 6, 757−762. (32) Zhang, C.; Losego, M. D.; Braun, P. V. Hydrogel-based glucose sensors: effects of phenylboronic acid chemical structure on response. Chem. Mater. 2013, 25, 3239−3250.

Eric Monflier graduated from the Ecole Nationale Supérieure de Chimie de Lille (ENSCL) in 1989 and received his Ph.D. degree from the University of Lille in 1992 under the supervision of Professor Francis Petit in the field of organometallic chemistry and homogeneous catalysis. In 1992, he became Associate Professor at the University of Artois where he set up an independent research group working on aqueous organometallic catalysis. He was promoted to Full Professor in 1996. His current research interests are mainly in the field of supramolecular catalysis and catalysis in multiphase systems. He is currently head of the Supramolecular Chemistry and Catalysis research team. He has authored more than 200 international scientific publications, 25 book chapters, and 12 patents.

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ABBREVIATIONS RAME-β-CD, randomly methylated β-cyclodextrin; PVCL, poly(N-vinylcaprolactam); DMU, N,N′-dimethylurea; NMU, N-methylurea; LMM, low-melting mixtures

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REFERENCES

(1) Kuntz, E. G. Homogeneous catalysis in water. CHEMTECH 1987, 17, 570−574. (2) Cornils, B.; Kuntz, E. G. Introducing TPPTS and related ligands for industrial biphasic processes. J. Organomet. Chem. 1995, 502, 177−186. (3) Hapiot, F.; Menuel, S.; Bricout, H.; Tilloy, S.; Monflier, E. Recent developments in cyclodextrin-mediated aqueous biphasic hydroformylation and Tsuji−Trost reactions. Appl. Organomet. Chem. 2015, 29, 580−587. (4) Hapiot, F.; Bricout, H.; Menuel, S.; Tilloy, S.; Monflier, E. Recent breakthroughs in aqueous cyclodextrin-assisted supramolecular catalysis. Catal. Sci. Technol. 2014, 4, 1899−1908. (5) Bricout, H.; Hapiot, F.; Ponchel, A.; Tilloy, S.; Monflier, E. Cyclodextrins as mass transfer additives in aqueous organometallic catalysis. Curr. Org. Chem. 2010, 14, 1296−1307. (6) Verspui, G.; Papadogianakis, G.; Sheldon, R. A.; Elbertse, G. Catalytic conversions in water. Part 19. Smooth hydroformylation of Nallylacetamide in mono- and biphasic aqueous media. J. Organomet. Chem. 2001, 621, 337−343. (7) Bauer, R. S.; Glockner, P. W.; Keim, W.; van Zwet, H.; Chung, H. Ethylene oligomerization. U.S. Pat. 3,644,563 (1972). (8) Jessop, P. G.; Leitner, W. In Chemical Synthesis Using Supercritical Fluids; Wiley- VCH: Weinheim, 1999. (9) Leitner, W. Supercritical carbon dioxide as a green reaction medium for catalysis. Acc. Chem. Res. 2002, 35, 746−756. (10) Jessop, P. G.; Ikariya, T.; Noyori, R. Homogeneous Catalysis in Supercritical Fluids. Chem. Rev. 1999, 99, 475−494. (11) Welton, T. Room-Temperature Ionic Liquids. Solvents for Synthesis and Catalysis. Chem. Rev. 1999, 99, 2071−2084. (12) Wasserscheid, P.; Keim, W. Ionic Liquids−New “Solutions” for Transition Metal Catalysis. Angew. Chem., Int. Ed. 2000, 39, 3772−3789. (13) Welton, T. Ionic liquids in catalysis. Coord. Chem. Rev. 2004, 248, 2459−2477. 3605


Perspective

ACS Sustainable Chemistry & Engineering (33) Ikeda, M.; Tanida, T.; Yoshii, T.; Hamachi, I. Rational Molecular Design of Stimulus-Responsive Supramolecular Hydrogels Based on Dipeptides. Adv. Mater. 2011, 23, 2819−2822. (34) Odriozola, I.; Loinaz, I.; Pomposo, J. A.; Grande, H. J. Gold− glutathione supramolecular hydrogels. J. Mater. Chem. 2007, 17, 4843− 4845. (35) Shen, J.-S.; Li, D.-H.; Cai, Q.-G.; Jiang, Y.-B. Highly selective iodide-responsive gel−sol state transition in supramolecular hydrogels. J. Mater. Chem. 2009, 19, 6219−6224. (36) Hapiot, F.; Menuel, S.; Monflier, E. Thermoresponsive Hydrogels in Catalysis. ACS Catal. 2013, 3, 1006−1010. (37) Escuder, B.; Rodríguez-Llansola, F.; Miravet, J. F. Supramolecular gels as active media for organic reactions and catalysis. New J. Chem. 2010, 34, 1044−1054. (38) Liu, Y.-R.; He, L.; Zhang, J.; Wang, X.; Su, C.-Y. Evolution of spherical assemblies to fibrous networked Pd(II) metallogels from a pyridine-based tripodal ligand and their catalytic property. Chem. Mater. 2009, 21, 557−563. (39) Zhang, J. Y.; Wang, X. B.; He, L. S.; Chen, L. P.; Su, C. Y.; James, S. L. Metal−organic gels as functionalisable supports for catalysis. New J. Chem. 2009, 33, 1070−1075. (40) He, X.; Aizenberg, M.; Kuksenok, O.; Zarzar, L. D.; Shastri, A.; Balazs, A. C.; Aizenberg, J. Synthetic homeostatic materials with chemomechano-chemical self-regulation. Nature 2012, 487, 214−218. (41) Potier, J.; Menuel, S.; Chambrier, M.-H.; Burylo, L.; Blach, J.-F.; Woisel, P.; Monflier, E.; Hapiot, F. Pickering emulsions based on supramolecular hydrogels: application to higher olefins’ hydroformylation. ACS Catal. 2013, 3, 1618−1621. (42) Aveyard, R.; Binks, B. P.; Clint, J. H. Emulsions stabilized solely by colloidal particles. Adv. Colloid Interface Sci. 2003, 100−102, 503−546. (43) Vignati, E.; Piazza, R.; Lockhart, T. P. Pickering emulsions: interfacial tension, colloidal layer morphology, and trapped-particle motion. Langmuir 2003, 19, 6650−6656. (44) Potier, J.; Menuel, S.; Monflier, E.; Hapiot, F. Synergetic Effect of randomly methylated β-cyclodextrin and a supramolecular hydrogel in Rh-catalyzed hydroformylation of higher olefins. ACS Catal. 2014, 4, 2342−2346. (45) Sueur, B.; Leclercq, L.; Sauthier, M.; Castanet, Y.; Mortreux, A.; Bricout, H.; Tilloy, S.; Monflier, E. Rhodium complexes non-covalently bound to cyclodextrins: novel water-soluble supramolecular catalysts for the biphasic hydroformylation of higher olefins. Chem. - Eur. J. 2005, 11, 6228−6236. (46) Chevry, M.; Vanbésien, T.; Menuel, S.; Monflier, E.; Hapiot, F. Tetronics/cyclodextrin-based hydrogels as catalyst-containing media for the hydroformylation of higher olefins. Catal. Sci. Technol. 2017, 7, 114. (47) Tan, S.; Ladewig, K.; Fu, Q.; Blencowe, A.; Qiao, G. G. Cyclodextrin-based supramolecular assemblies and hydrogels: recent advances and future perspectives. Macromol. Rapid Commun. 2014, 35, 1166−1184. (48) Larrañeta, E.; Isasi, J. R. Self-assembled supramolecular gels of reverse poloxamers and cyclodextrins. Langmuir 2012, 28, 12457− 12462. (49) Léger, B.; Menuel, S.; Ponchel, A.; Hapiot, F.; Monflier, E. Nanoparticle-based catalysis using supramolecular hydrogels. Adv. Synth. Catal. 2012, 354, 1269−1272. (50) Taira, T.; Suzaki, Y.; Osakada, K. Hydrogels composed of organic amphiphiles and α-cyclodextrin: supramolecular networks of their pseudorotaxanes in aqueous media. Chem. - Eur. J. 2010, 16, 6518− 6529. (51) Denicourt-Nowicki, A.; Ponchel, A.; Monflier, E.; Roucoux, A. Methylated cyclodextrins: an efficient protective agent in water for zerovalent ruthenium nanoparticles and a supramolecular shuttle in alkene and arene hydrogenation reactions. Dalton Trans. 2007, 5714− 5719. (52) Wang, M.; Wang, J.; Wang, Y.; Liu, C.; Liu, J.; Qiu, Z.; Xu, Y.; Lincoln, S. F.; Guo, X. Synergetic catalytic effect of α-cyclodextrin on silver nanoparticles loaded in thermosensitive hydrogel. Colloid Polym. Sci. 2016, 294, 1087−1095.

(53) Jia, H.; Schmitz, D.; Ott, A.; Pich, A.; Lu, Y. Cyclodextrin modified microgels as “nanoreactor” for the generation of Au nanoparticles with enhanced catalytic activity. J. Mater. Chem. A 2015, 3, 6187−6195. (54) Bai, J.; Yang, Q. B.; Li, M. Y.; Wang, S. G.; Zhang, C. Q.; Li, Y. X. Preparation of composite nanofibers containing gold nanoparticles by using poly(N-vinylpyrrolidone) and β-cyclodextrin. Mater. Chem. Phys. 2008, 111, 205−208. (55) Huang, T.; Meng, F.; Qi, L. M. Facile synthesis and onedimensional assembly of cyclodextrin-capped gold nanoparticles and their applications in catalysis and surface-enhanced Raman scattering. J. Phys. Chem. C 2009, 113, 13636−13642. (56) Sau, T. K.; Pal, A.; Jana, N. R.; Wang, Z. L.; Pal, T. Size controlled synthesis of gold nanoparticles using photochemically prepared seed particles. J. Nanopart. Res. 2001, 3, 257−261. (57) Zhang, Q. H.; Vigier, K. D.; Royer, S.; Jérôme, F. Deep eutectic solvents: syntheses, properties and applications. Chem. Soc. Rev. 2012, 41, 7108−7146. (58) Imperato, G.; Eibler, E.; Niedermaier, J.; König, B. Low-melting sugar−urea−salt mixtures as solvents for Diels−Alder reactions. Chem. Commun. 2005, 1170−1172. (59) Russ, C.; Ilgen, F.; Reil, C.; Luff, C.; Haji Begli, A.; König, B. Efficient preparation of β-D-glucosyl and β-D-mannosyl ureas and other N-glucosides in carbohydrate melts. Green Chem. 2011, 13, 156−161. (60) Imperato, G.; Hoger, S.; Lenoir, D.; König, B. Low melting sugar− urea−salt mixtures as solvents for organic reactionsestimation of polarity and use in catalysis. Green Chem. 2006, 8, 1051−1055. (61) Imperato, G.; Vasold, R.; König, B. Stille Reactions with tetraalkystannanes and phenyltrialkylstannanes in low melting sugarurea-salt mixtures. Adv. Synth. Catal. 2006, 348, 2243−2247. (62) Ilgen, F.; König, B. Organic reactions in low melting mixtures based on carbohydrates and L-carnitinea comparison. Green Chem. 2009, 11, 848−854. (63) Jérôme, F.; Ferreira, M.; Bricout, H.; Menuel, S.; Monflier, E.; Tilloy, S. Low melting mixtures based on β-cyclodextrin derivatives and N,N′-dimethylurea as solvents for sustainable catalytic processes. Green Chem. 2014, 16, 3876−3880. (64) Hapiot, F.; Leclercq, L.; Azaroual, N.; Fourmentin, S.; Tilloy, S.; Monflier, E. Rhodium-catalyzed hydroformylation promoted by modified cyclodextrins: current scope and future developments. Curr. Org. Synth. 2008, 5, 162−172. (65) Ferreira, M.; Jérôme, F.; Bricout, H.; Menuel, S.; Landy, D.; Fourmentin, S.; Tilloy, S.; Monflier, E. Rhodium catalyzed hydroformylation of 1-decene in low melting mixtures based on various cyclodextrins and N,N′-dimethylurea. Catal. Commun. 2015, 63, 62−65. (66) Zhao, X.; Liu, X.; Lu, M. β-cyclodextrin-capped palladium nanoparticle-catalyzed ligand-free Suzuki and Heck couplings in lowmelting β-cyclodextrin/NMU mixtures. Appl. Organomet. Chem. 2014, 28, 635−640.

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Catalysis in Cyclodextrin-Based Unconventional Reaction Media

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