Application Of Proline Ionic Liquid In Asymmetric Organic Synthesis

Organocatalysis has become a field of central importance for the asymmetric synthesis of chiral molecules. Novel modes of substrate activation have been achieved using organocatalysts that can now deliver unique, orthogonal, or complementary selectivities comparable to many established metal-catalyzed transformations. Notably, proline has been gradually recognized as a simple, commercial and cheap chiral catalyst for many asymmetric organic reactions. The use of simple proline as catalyst for asymmetric organic reactions at the beginning of this century became a milestone in the growth of organocatalysis as a useful synthetic strategy.In the recent years, ionic liquids are attracting considerable attention as reaction solvents and catalysts for their remarkable properties, including a negligibly small vapor pressure, high thermal stability, immiscibility with most organic/inorganic solvents, high ionic conductivity and easily recovered by careful washing in ether or pentane.Among the various ionic liquids, chiral ionic liquids are particularly attractive and important for their widespread potential applications in asymmetric synthesis. Some derived from natural amino acids, which have shown to serve as effective catalysts. Amino acid ionic liquids have mostly been designed using a series of cationic derivatives due to their convenient chemical modification, but there is much less information about the effect of anion structure.Therefore, we first employed proline anion as an effective module with ionic liquid for the asymmetric Mannich reaction, Diels-Alder reaction and Aldol reaction. Different solvents, reaction temperatures and the ratio of catalyst were investigated in these reactions. Under optimal conditions, high enantio-and diastereoselectivities compounds have been achieved. Most importantly, regarding to atom economy and green chemistry, this efficient system can be reused more than 4 runs in Diels-Alder reaction and Aldol reaction.