Divergent Rh Catalysis: Asymmetric Dearomatization Versus C–H Activation Initiated by C–C Activation

The divergent catalytic reactions based on C–C activation of benzocyclobutenones have been discovered, consisting of a highly enantioselective dearomatic "Cut & Sew" transformation and a cascade C–C/C–H activation/annulation process. The asymmetric dearomatization was achieved with 2.5 mol % [Rh(HQ)(cod)]BF4 and 3 mol % (S)-dtbm-Segphos, leading to a variety of highly enantioenriched polyfused rings (21 examples, up to 99% yield and 99% enantiometric excess (ee)). While the tandem C–C/C–H activation yields a series of amide-linked biaryl tricycles (29 examples, up to 89% yield) through a net C1–C2 bond and Caryl–H bond metathesis. A detailed density functional theory (DFT) computation revealed that an amide-directed regioselective C1–C2 activation with Rh complex is realized, in contrast to the known C1–C8 cleavage. The origins of asymmetric dearomatization were further elucidated.