Asymmetric organocatalyzed reaction sequence of 2-hydroxy cinnamaldehydes and acyclic N-sulfonyl ketimines to construct diverse chiral bridged polycyclic aminals

Abstract

Asymmetric organocatalytic annulation reactions have been developed, where both 2-hydroxy cinnamaldehydes and acyclic N-sulfonyl ketimines were used as multisite substrates (more than two reactive sites) in an iminium catalysis triggered sequential process. Notably, H₂O is crucial for reactivity and selectivity, since different isolable hemiaminal intermediates were obtained in aqueous medium, thus leading to diverse chiral bridged polycyclic aminals in a highly regio- and stereoselective manner. Several other interesting transformations with the obtained aminals were also realized.