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

The synthesis, characterization, and evaluation of a new highlyefficient organocatalyst, namely, (5S)-2,2,3-trimethyl-5-thiobenzylmethyl-4-imidazolidinone hydrochloride, has beenachieved. The catalyst possesses important structural featuresthat should increase the catalytic efficiency and solubility inpolar media. The application of the ionic-liquid-supported imidazolidinonecatalyst in enantioselective Diels–Alder reactionswas investigated. The Diels–Alder reactions of several dienesand dienophiles proceeded efficiently in the presence of thecatalyst to provide the desired products in moderate to goodyields and from good to excellent enantioselectivities. The conformationstudy confirms that in the transition state the Reface is shielded completely by the phenyl ring and an approachon the less hindered Si face is preferred. Particularly remarkableis the fact that the entire ionic liquid/HCl 0.01m/catalystsystem can be recovered and reused in up to six runs withoutan appreciable loss of catalytic activity.