Intramolecular and intermolecular benzannulation of arylethanone derivatives enabled by visible light-induced catalytic generation of tether-tunable distonic radical anions

Abstract

Polarity umpolung has emerged as an indispensable tool to achieve remarkable reactivity and expanded chemical space by overcoming the limitations of innate polarity. Although radical-based synthetic transformations often involve umpolung with two-electron processes because of the different electronic properties of closed-shell and open-shell functional groups, the development and application of polarity regulation between radical species remain challenging and mechanistically poorly understood. Herein, we introduce a novel approach by harnessing catalytically generated tether-tunable distonic radical anions (TDRAs) to realize intramolecular or intermolecular benzannulation of arylethanone derivatives through the formation of 1,3-dicarbonyl radical intermediates. Applying this operationally simple, visible-light-induced modular platform, more than 60 examples are presented to establish the generality of this process with broad functional group tolerance. Experimental and computational mechanistic studies demonstrate that the key to the success of this transformation heavily relies on the philicity umpolung and conformational restriction from nucleophilic TDRAs in the basic asynchronous proton-coupled electron transfer (PCET) mechanism for enabling the generation of electrophilic alkyl radicals.