Visible Light Induced Photocatalyst‐Free C−X (X=B, C, O, P,S, Se) Bond Formation of Aryl Halides

Abstract

Aryl halides are one of the most important chemical feedstocks in pharmaceuticals due to its easy accessibility, inexpensiveness, and widely utilized as aryl radical precursors in organic synthetic chemistry. Conventionally, the stoichiometric reagents such as AIBN/n‐Bu3SnH were used for generation of aryl radical from aryl halides, and suffered from requirement of toxic radical initiators, high temperature and thus, the development of simple, mild strategies for the generation of aryl radical from aryl halides are highly desirable. Recently, visible light mediated strategies received considerable attention, allowing the generation of aryl radical from aryl halides under mild reaction conditions. The present review described the recent breakthroughs and advancements in visible light mediated photocatalyst‐free C‐B/C/O/P/Se/S bond formation of aryl halides.

Electroreduction strategy: a sustainable tool for the generation of aryl radicals

“…14 In recent years, the reductive dehalogenation of aryl halides has proved to be a productive synthetic strategy for producing aryl radicals. 3 Frequently, aryl halides have higher reduction potentials, especially aryl chlorides and fluorides, making their single-electron reduction extremely difficult (Scheme 2). 15 Therefore, it is still a formidable challenge to realize the downstream functionalization of inert aryl halides.…”

“…The aryl radical-mediated reductive functionalization of aryl halides has been extensively studied, and offers a practical and straightforward avenue for the construction of structurally diverse functionalized arenes. 3,25 Recently, numerous synthetic chemists have exploited green electroreductive dehalogenation strategies to achieve the multifarious conversion of aryl radicals, which frequently serve as ideal complements to transition-metal-catalyzed arylation reactions.…”

“…1 Since the advent of the Meerwein arylation reaction in the 1940s, 2 a considerable number of synthetic chemists have employed the conversions of aryl radicals as ideal supplements to transition-metal-catalyzed arylation reactions, which has yielded novel, promising alternatives for the introduction of aryl and heteroaryl moieties into molecular scaffolds. Various compounds, such as aryl halides, 3 aryl diazonium salts, 4 aryl carboxylic acids, 5 aryl triflates, 6 hypervalent iodine( iii ) reagents, 7 aryl borates, 8 and aryl sulfonium salts, 9 have been successfully used as aryl radical precursors.…”