Progresses in organocatalytic asymmetric dearomatization reactions of indole derivatives
Chiral indole derivatives such as indolines and indolenines are important heterocyclic frameworks which constitute the core structures of many natural products and bioactive molecules. So, intensive attentions from chemists have been paid to the construction of such frameworks. Among different approaches, organocatalytic asymmetric dearomatization (organo-CADA) reactions of indole derivatives have become powerful methods toward this goal. Consequently, a variety of enantioenriched heterocyclic frameworks containing indoline, indolenine and the related cores have been constructed via organo-CADA reactions of indole derivatives, and a series of important natural products with structural complexity and enantiopurity have been synthesized based on these methodologies. This review summarizes the progresses in organo-CADA reactions of indole derivatives since 2004 and their applications in total synthesis of natural products, and gives some insights into challenging issues in this research field, which will enlighten the future development of this field.