Recent Advances in Enantioselective Brønsted Base Organocatalytic Reactions

Enantioselective Brønsted base catalyzed reactions have established themselves as powerful tools for the construction of optically pure compounds. Most strategies aim at improving these reactions involve the modification of substrates to decrease the pK a of the acidic proton. Typically, an electron-withdrawing group such as an ester or a fluorine is placed at the α-carbon, where the proton is also residing. The activation of less active proton, thus, becomes a major challenge in this field of research. In order to overcome this pK a barrier, some new innovative approaches have been demonstrated in recent years. The implementation of dual activation modes and the development of organocatalytic Brønsted superbases are selected to be discussed in this minireview.1 Introduction2 Dual Activation Using Lewis Acid and Brønsted Base3 Dual Activation Using Iminium Catalyst and Brønsted Base4 Chiral Brønsted Superbase5 Chiral Ion-Pair Brønsted Base6 Summary and Outlook