Organocatalytic Asymmetric Arylative Dearomatization of 2,3-Disubstituted Indoles Enabled by Tandem Reactions

The organocatalytic asymmetric arylative dearomatization of indoles was achieved through two tandem approaches involving 2,3‐disubstituted indoles and quinone imine ketals. One approach utilized the enantioselective cascade 1,4 addition/alcohol elimination reaction, the other employed the one‐pot tandem arylative dearomatization/transfer hydrogenation sequence. In both cases, enantiomerically pure indole derivatives that bear an all‐carbon quaternary stereogenic center were generated in high yields and excellent stereoselectivities (all d.r.>95:5, up to 99 % ee). Less aromatic: The title reaction between indoles and quinone imine ketals was achieved by the two tandem approaches shown in the scheme. In both cases, enantiomerically pure indole derivatives bearing an all‐carbon quaternary stereogenic center were generated in high yields and excellent stereoselectivities.