Efficient Organocatalyst Supported on a Simple Ionic Liquid as a Recoverable System for the Asymmetric Diels–Alder Reaction in the Presence of Water

Abstract

The synthesis, characterization, and evaluation of a new highly efficient organocatalyst, namely, (5S)‐2,2,3‐trimethyl‐5‐thiobenzylmethyl‐4‐imidazolidinone hydrochloride, has been achieved. The catalyst possesses important structural features that should increase the catalytic efficiency and solubility in polar media. The application of the ionic‐liquid‐supported imidazolidinone catalyst in enantioselective Diels–Alder reactions was investigated. The Diels–Alder reactions of several dienes and dienophiles proceeded efficiently in the presence of the catalyst to provide the desired products in moderate to good yields and from good to excellent enantioselectivities. The conformation study confirms that in the transition state the Re face is shielded completely by the phenyl ring and an approach on the less hindered Si face is preferred. Particularly remarkable is the fact that the entire ionic liquid/HCl 0.01 M/catalyst system can be recovered and reused in up to six runs without an appreciable loss of catalytic activity.

A High Loading and Recyclable Pentaerythritol Supported Imidazolidin-4-one Catalyst for Enantioselective Diels–Alder Reactions

“…However, its practical use in reactions is still hindered due to the need for high catalyst loading and difficulties in recovering the catalyst from the reaction mixture. One obvious way to overcome these problems is to immobilizing or attaching the catalyst unit on a recyclable support , such as PEG [11], dendrimer [12,13], siliceous and polymer-coated mesocellular foam (MCF) [14], fluorous tag [15], poly(-methyl-hydrosiloxane) (PHMS) [16], ionic liquid [17][18][19][20].…”

“…Pentaerythritol is a well known, cheap, atoxic, widely used chemical raw materials, and it is considered to be ideal building blocks in many areas of materials chemistry [32][33][34] and in the synthesis of dendrimers [35][36][37]. Because of its low molecular weight and its special molecular structure, the loading capacity of pentaerythritol is higher than many other kind of supports such as traditional polymer support [10-12, 14, 16, 22], ionic liquid [17][18][19][20] and tetraarylphosphonium salt [28,29]. Owing to its dendrimer-like structure, we believe that pentaerythritol used as a support not only can solve the problem of recovering which meet the requirement of modern green chemistry for sustainability, but also may enhance the catalytic performance like traditional dendrimer supports do, even without generation growing.…”

“…Next, the effects of reaction temperature in the DielsAlder reaction was investigated (Table 1, entries [16][17][18][19][20][21]. Among the temperature examined, 25°C provided the best yield and comparative stereoselectivity, and it is the best control temperature, so 25°C is the best candidate for the Diels-Alder reaction.…”

Montmorillonite K10-Catalyzed Solvent-Free Conversion of Furfural into Cyclopentenones

“…Different studies have encouraged the use of unconventional methods or "green" solvents [8], principally water [8][9][10][11][12][13][14][15], ionic liquids [16][17][18][19][20], deep eutectic solvents [21][22][23][24], or bio-solvents [25][26][27][28][29][30], but the use of solvent-free conditions [31][32][33][34][35][36] is certainly the best choice to conduct eco-sustainable chemical procedures. A solvent-free reaction can be performed by using the reactants alone, or incorporating them in solid supports simplifying the experimental and work-up procedures, and considerably lowering the environmental impact.…”

Montmorillonite K10-Catalyzed Solvent-Free Conversion of Furfural into Cyclopentenones

“…A solvent-free reaction may be carried out using the reactants alone or incorporating them in solid supports simplifying the experimental and work-up procedures lowering considerably environmental impact. These would be particularly important in the industrial manufactures where, in the last decades, the use of microwave heating among others [37][38][39][40], was proposed in solvent-free chemical processes catalyzed by solid Lewis acids as useful method for increasing the reaction rate, simplifying the work-up and improving yield [41][42][43][44].…”