Combining prolinamides with 2-pyrrolidinone: Novel organocatalysts for the asymmetric aldol reaction

Peptides and especially prolinamides have been identified as excellent organocatalysts for the aldol reaction. The combination of prolinamides with derivatives bearing the 2-pyrrolidinone scaffold, deriving from pyroglutamic acid, led to the identification of novel organocatalysts for the intermolecular asymmetric aldol reaction. The new hybrids were tested both in organic and aqueous media. Among the compounds tested, 22 afforded the best results in petroleum ether, while 25 afforded the products in brine in high yields and selectivities. Then, various ketones and aldehydes were utilized and the products of the aldol reaction were obtained in high yields (up to 100%) with excellent diastereo- (up to 97:3 dr) and enantioselectivities (up to 99% ee).