Asymmetric Synthesis of Heterohelicenes via Cobalt-Catalyzed Enantioselective C–H Activation

Abstract Helicenes, characterized by their helical chirality stemming from ortho-fused aromatic rings, are pivotal for applications in asymmetric catalysis, biological chemistry, and materials science. Their catalytic asymmetric synthesis, however, remains underdeveloped, lagging far behind that of central and axial chiral compounds. Herein, we develop a cobalt/salicyloxazoline-catalyzed enantioselective C–H activation/annulation method for the efficient assembly of heterohelicenes, by designing the specialized arylamide substrate featuring a benzo-3,4-phenanthrene framework. Under mild conditions with O2 as the oxidant, this protocol accommodates diverse arylamide, internal/terminal alkynes, and allenes with high efficiency and stereoselectivity, affording a series of chiral isoquinolinone-fused [5]helicenoids with good configurational stability (ΔG≠ up to 30.8 kcal/mol). The practicality is further validated through scale-up reactions, synthetic transformation, and asymmetric catalysis. Experimental and computational investigations provide in-depth insight into the catalytic mechanism. Notably, these optically pure heterohelicenes demonstrate potential CPL performance (glum up to 3.4 × 10–3), underscoring the significance of this protocol.