Atroposelective Synthesis of 3,3'-Bisindoles Bearing Axial and Central Chirality: Using Isatin-Derived Imines as Electrophiles

.Summary of main observation and conclusion An atroposelective synthesis of a new class of 3,3'-bisindoles bearing axial and central chirality has been established via catalytic asymmetric addition reactions using isatin-derived imines as electrophiles (23 examples, up to 80% yield, > 95 : 5 dr, 98 : 2 er). This approach takes advantage of chiral phosphoric acid-catalyzed dynamic kinetic resolution of 2-substituted 3,3'-bisindoles via nucleophilic addition of such substrates with isatin-derived imines. In this approach, isatin-derived imines acted as a class of competent electrophiles due to their high reactivity and bulky size, which provided an easy access to axially chiral 3,3'-bisindoles incorporated with a biologically important chiral 3-aminooxindole unit. This approach has greatly expanded the generality and applicability of the strategy of dynamic kinetic resolution for the synthesis of enantioenriched 3,3'-bisindole derivatives bearing both axial and central chirality.