A case of chain propagation: α-aminoalkyl radicals as initiators for aryl radical chemistry
The generation of aryl radicals from the corresponding halides by redox chemistry is generally considered a difficult task due to their highly negative reduction potentials. Here we demonstrate that α-aminoalkyl radicals can be used as both initiators and chain-carriers for the radical coupling of aryl halides with pyrrole derivatives, a transformation often employed to evaluate new highly reducing photocatalysts. This mode of reactivity obviates for the use of strong reducing species and was also competent in the formation of sp2 C-P bonds. Mechanistic studies have delineated some of the key features operating that trigger aryl radical generation and also propagate the chain process.
Constantin, Timothée,Juliá, Fabio,Leonori, Daniele,Sheikh, Nadeem S.
p. 12822 - 12828
(2020/12/29)
Radical Arylation of Anilines and Pyrroles via Aryldiazotates
The radical arylation of anilines and pyrroles can be achieved under transition-metal- and catalyst-free conditions by using aryldiazotates in strongly alkaline aqueous solutions. The aryldiazotates act as protected diazonium ions, which do not undergo azo coupling with electron-rich aromatic substrates, but can still serve as an aryl radical source at slightly elevated temperatures. Based on an improved preparation of aryldiazotates in aqueous solution, homolytic aromatic substitutions of anilines and pyrroles were conducted with good overall yields and high regioselectivity. Moreover, DFT calculations provided further mechanistic insights.
Hofmann, Josefa,Gans, Eva,Clark, Timothy,Heinrich, Markus R.
p. 9647 - 9656
(2017/07/22)
Room-temperature arylation of arenes and heteroarenes with diaryliodonium salts by photoredox catalysis
Aryl radicals produced by irradiation of diaryliodonium salts with visible light under the catalysis of [Ru(bpy)3]2+ undergo coupling with a wide range of arenes and heteroarenes, affording various biaryls through direct C-H arylation at room temperature. Georg Thieme Verlag Stuttgart · New York.