“Highly Enantioselective and Recyclable Organocatalytic Systems for Asymmetric Reactions.”
A major problem associated with the use of present catalysts for asymmetric transformations in organic synthesis is that they are not easily recovered and recycled because they are typically soluble in the reaction media. As a result, large amounts of catalysts are typically used, especially in industry, which poses a disposal problem. Our research group has developed various recyclable homogeneous organocatalysts that are unique in that they contain ionic liquid moieties, which convey a wide range of properties to the catalysts. As a result, these ionic liquid-supported (ILS) organocatalysts are tunable and their properties can be adjusted to meet a wide variety of reaction conditions. Hence, by changing the polarity of the reaction media after a reaction is complete, the product phase can be separated from the catalyst phase, which makes for easy separation of the catalyst from the products to make the catalyst readily recyclable. Since these catalysts are recyclable and effective in aqueous solvents, they also provide a “green’ alternative. These organocatalysts are used to catalyze various asymmetric carbon-carbon reactions, including the Baylis Hillman, aldol and Michael reactions, and for most of the reactions studied, excellent enantioselectivities and diastereoselectivities are obtained and the catalysts could be recycled several times.