Organocatalytic enantioselective reactions involving prochiral carbocationic intermediates.

Since the discovery of carbocations in 1901, the past 120 years have witnessed many marvelous advances in the chemistry of carbocations. The state-of-the-art research in this field is to overcome the intrinsic instability and high reactivity of the prochiral carbocationic intermediates to develop catalytic asymmetric reactions. Such transformations enable the facile synthesis of structurally diverse value-added products from readily available starting materials such as alkenes, alcohols, and carbonyl derivatives, and enjoy high and even perfect atom-economy in most cases. Notably, such allows catalytic stereoconvergent synthesis from racemic substrates and can realize regioselectivity in olefin functionalization reactions complementary to radical processes. With the rapid developments in modern asymmetric organocatalysis, a variety of highly enantioselective protocols evolving prochiral carbocationic intermediates have been achieved by employing three strategies, namely chiral ion-pairing, chiral nucleophile, or chiral carbenium ion strategy. This feature article aims to summarize the exciting advances in this emerging area and briefly showcase the possible mechanisms. The advantages and limitations of each strategy are presented as well as their synthetic applications in the synthesis of natural products or bioactive compounds.