Substrate- and Catalyst-Controlled Chemodivergent [3+2] Cycloaddition of 2-Substituted 3-Styrylindoles With...

Chiral phosphoric acid (CPA)-catalyzed [3+2] cycloaddition of azonaphthalenes with 3-vinylindoles is known to furnish C-selective dihydrobenzo[e]indoles. We show here that installation of a substituent at C2 of the styrylindole partner unlocks a chemodivergent manifold in which both substrate sterics and catalyst structure govern C- versus N-selective annulation. Under A2 catalysis, minimally hindered substrates remain on the established C-selective pathway, whereas more sterically demanding partners are diverted to a complementary N-selective process. For these hindered substrates, switching to the anthryl-substituted CPA A4 reverses the chemoselectivity and restores efficient C-selective cycloaddition. Across the two manifolds, structurally diverse annulation products are obtained in good to excellent yields and enantioselectivities. The N-selective adducts further undergo DDQ-mediated central-to-axial chirality conversion to furnish configurationally stable bisindole atropisomers in high yields and excellent chirality-conversion percentages.