Organocatalytic enantioselective conjugate addition of aldehydes to maleimides in deep eutectic solvents

Abstract

The conjugate enantioselective addition of aldehydes, mainly α,α-disubstituted, to maleimides leading to enantioenriched succinimides, has been achieved in recyclable deep eutectic solvents at room temperature. Enantiomerically pure carbamate-monoprotected trans-cyclohexane-1,2-diamines are used as organocatalysts, affording high yields and up to 94% ee of the final succinimides. The product can be extracted from the deep eutectic solvent, which retains the chiral organocatalyst, allowing both the solvent and catalyst to be reused.