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).