Cobalt/Organophotoredox Dual-Catalysis-Enabled Cyclization of 1,5,10-Enediynes Involving Metallole-Mediated Remote C(sp3)–H Bond Activation Leading to Axially Chiral Aryl Alkenes
Transition-metal-catalyzed C(sp3)–H functionalization has been much less investigated compared to C(sp2)–H functionalization because the site-selectivity control in C(sp3)–H bond activation is much more challenging than that in C(sp2)–H bond activation. Site-selective C(sp3)–H functionalization without the assistance of directing groups is highly desirable, because the installation and removal of directing groups are not required. Hence, cycloaddition through a site-selective C–H bond activation triggered by the formation of metallacycles, such as metalloles, is a highly atom- and step-economical method for synthesizing complex carbo- and heterocycles from simple unsaturated substrates. Herein, we report the cobalt/photoredox dual-catalysis-enabled cyclization of 1,5,10-enediynes via remote C(sp3)–H bond activation triggered by metallole formation, affording axially chiral aryl alkenes. Several control experiments and theoretical calculations suggest that the C(sp3)–H bond cleavage proceeds through σ-complex-assisted metathesis (σ-CAM) in the metallole intermediate.journal articl
