Supramolecular Interactions Based on Ionic Liquids for Tuning of the Catalytic Efficiency of (l)-Proline

Abstract

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Catalysis in Supramolecular Systems: the Case of Gel Phases

“…Evidences about the favourable effect that the three-dimensional network of a gel phase can exert on the outcome of the aldol reaction have been also reported in the case of soft materials formed in ionic liquid solution. [24] Indeed, in the attempt to optimize conditions of the reaction between acetone and p-nitrobenzaldehyde, in the presence of L-proline, the formation of ionogel phase was observed when a weight ratio Interestingly, in gel phase the reaction proceeded with 90 % of yield and 62 % of ee. This result was ascribed to the supramolecular structure formed by the interactions established among L-proline and ions constituting the ionic liquid, that provide the appropriate mass transfer for the catalytic process.…”

Chiral Imidazolium Prolinate Salts as Efficient Synzymatic Organocatalysts for the Asymmetric Aldol Reaction

“…The selectivity (96%) and enantioselectivity (64%) for the prolinate of this racemic cation indicate that the ( R , R )- trans -Cy6-OH-Im-Bu- l -Pro organocatalyst displays a high activity, selectivity, and enantioselectivity, suggesting the presence of a “ match/mismatch ” effect between the configuration of the C-OH carbon atom and the one of l -prolinate. Related “ match/mismatch ” effects have been reported for asymmetric catalytic systems containing two chiral components, as is the case in the use of chiral cocatalysts, chiral activators, or two chiral ligands in catalytic metal complexes [ 32 , 46 , 47 , 48 , 49 , 50 ].…”

“…Recently, a variety of imidazolium ILs, including chiral and nonchiral compounds, have been studied as efficient reaction media or additives for the aldol reaction catalyzed by l -proline, with the results highlighting the importance of the involved supramolecular noncovalent interactions [ 30 , 31 , 32 ]. These results suggested the presence of well-defined supramolecular structures based on the correct disposition, including the correct configuration, of the functional elements located in the different components assembled.…”

Concerted Catalysis by Nanocellulose and Proline in Organocatalytic Michael Additions

“…Much effort has been concentrated on remedying these issues by designing more efficient catalysts that are derived from the proline structure [21,30,31], or by pairing proline with small organic molecules to form significantly more active complexes [32,33]. Methods using ionic liquids as solvents [34,35] and covalent anchoring to polymers, such as polyethylene glycol or polystyrene, to allow catalyst recovery, have also been investigated [36,37]. However, these strategies require additional catalyst preparation steps, resulting in additional costs that hamper their industrial application.…”