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.