Catalyst-free intramolecular radical cyclization cascades initiated by the direct homolysis of Csp3–Br under visible light

Abstract

A visible light-driven carbon–carbon bond-forming cyclization cascade under metal- and catalyst-free conditions has been reported. The cascade is initiated through a transient alkyl radical intermediate that is formed by the direct homolysis of C_sp³–Br under visible light, affording a series of 3-substituted chroman-4-ones. Crucially, this work exhibited a facile and effective strategy for building three-dimensional polycyclic compounds using two-dimensional long-chain compounds as building blocks. The protocol has significant advantages such as high diastereoselectivity, high regioselectivity, metal- and catalyst-free, mild reaction conditions, controllable synthesis, and operational simplicity.