Enantioselective copper-catalyzed dearomative borylative cyclization of indoles and mechanistic insights

Alicyclic nitrogen heterocycles, such as enantioenriched polycyclic fused [1,2-a]indoline derivatives, are widespread in natural products, agrochemicals and pharmaceutical agents. Existing methods predominantly rely on the recent emerging Heck-type catalytic asymmetric dearomatization（CADA） protocol, wherein noble palladium catalysts commonly necessitate the form arylPd species-triggered these transformations. In contrast, a more sustainable base metal catalysis paradigm through alkyl metal species disrupting the aromaticity, that is, the utilization of challenging asymmetric Csp3–Csp3 bond formation entry to such important chiral densely functionalized polycyclic molecular scaffolds, remains an elusive task. Herein, we report the first copper-catalyzed dearomative borylative cyclization of indoles under mild reaction conditions, affording an array of valuable Bpin-containing pyrrolo-fused [1,2-a]indolines bearing four consecutive stereogenic centers with excellent enantioand diastereoselectivity. The synthetic potential was documented via an array of useful transformations. Density functional theory（DFT） calculation studies elucidated the origin of the chemo-, regio-, enantio-and diastereoselectivities of this conversion.