Generation of Photoinduced Phenalenyl-Based Radicals: Towards Designing Reductive C−C Coupling Catalysis

Abstract

Organic photoredox catalysis is a versatile tool for accessing a wide range of synthetic transformations. Towards the development of a new class of organophotoredox catalysts, we have employed phenalenyl, an odd alternant hydrocarbon (OAH), for reductive C−C coupling reactions. Phenalenyl can adopt a stable open-shell state (radical), using its non-bonding molecular orbital. To date, chemically induced phenalenyl-based radicals have been extensively explored in designing various intriguing organic materials and recently towards electron transfer catalysis. However, the photochemical generation of phenalenyl-based radicals is rare. In this work, we report the photoinduced generation of phenalenyl-based radicals with detailed mechanistic studies such as steady-state absorption, time-resolved transient absorption spectroscopy, and in-situ absorption kinetic experiments to authenticate the generation of photo-induced phenalenyl radicals. In addition, we present results demonstrating that this novel catalytic species can be applied to reductive pinacol coupling catalysis and reductive alkylation of terminal alkynes.