Divergent Rh Catalysis: Asymmetric Dearomatization Versus C–H Activation Initiated by C–C Activation
Xiaotong Li, Lingfei Hu, Shuo Ma, Haiyong Yu, Gang Lü, Tao Xu
Abstract
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)]BF 4 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 C 1 –C 2 bond and C aryl –H bond metathesis. A detailed density functional theory (DFT) computation revealed that an amide-directed regioselective C 1 –C 2 activation with Rh complex is realized, in contrast to the known C 1 –C 8 cleavage. The origins of asymmetric dearomatization were further elucidated.