Catalytic Asymmetric Reactions with N , O -Aminals

N, O -aminals, molecules bearing a geminally N, O -substituted (stereogenic) carbon center, have been recently recognized as an important class of building blocks in organic synthesis. As direct precursors of imines and iminium ions, N, O -aminals were converted through asymmetric organocatalysis or metal catalysis to diverse enantiomerically enriched compounds including N -heterocycles. Furthermore, cyclic N, O -hemiaminals acted as acyclic amino aldehyde surrogates, which were transformed to enantioenriched products otherwise challenging to access. Finally, cyclic N, O -aminals were formed in situ as key intermediates in asymmetric catalysis. In this review, we introduce a wide array of catalytic asymmetric protocols involving the use of four distinct types of N, O -aminals as starting materials or key intermediates.