Mechanism-controlled switchable regioselective O- and N-cyclization alkenylation of alkenylbenzamides via dual photoredox and cobalt catalysis

Abstract

In the context of green chemistry, reliable and predictable photocatalysis-based switchable divergent synthesis that produces multiple regioisomers starting from identical raw materials is desirable. In this study, we developed a dual organic photoredox and cobalt-catalyzed, acceptorless switchable regioselective O- and N-cyclization alkenylation of alkenylbenzamides. The key focus lies in controlling the reaction pathway, specifically, to achieve the formation of alkene-derived radical cations and the process of proton-coupled electron transfer (PCET) by regulating the redox potential matching between the substrate active groups and photocatalytic systems. This approach afforded high regioselectivity in the synthesis of alkenyl iminolactone and lactam compounds from the same alkenylbenzamide raw materials while maintaining excellent step- and atom-economy. Notably, this method eliminates the need for stoichiometric oxidants and the prefunctionalization of alkenes, generating H₂ as the sole waste. Moreover, a scale-up reaction using the continuous-flow technology further demonstrated the practicality and utility of this strategy.