Single Electron Activation of Aryl Carboxylic Acids

Abstract

Aryl carboxylic acids are stable and readily available in great structural diversity both from natural and well-established synthetic procedures, which make them promising starting materials in organic synthesis. The conversion of benzoic acids into high-value molecules is of great importance and have gained much interest of synthetic chemists. The recent development of single-electron (1e À ) activation strategy has been esteemed as a complementary method for the transformation of benzoic acids. In this context, carboxylate groups can be selectively transferred into reactive aryl carboxylic radical, aryl radical, and acyl radical by electrocatalysis, photocatalysis, or in the presence of some SET oxidants. Based on these radical species, remarkable advancements have been achieved for the rapid formation of various chemical bonds over the past 10 years. In this review, we summarize recent advances in single electron activation of aryl carboxylic acids, with an emphasis on reaction scope, catalytic system, limitation, and underlying reaction mechanism.

A case of chain propagation: α-aminoalkyl radicals as initiators for aryl radical chemistry

“…Aer identifying optimal reaction conditions, we explored the scope of the transformation by evaluating different aryl halides (Scheme 4A). Aryl iodides substituted with electron withdrawing groups at the para-position reacted in good to high yields (3,(7)(8)(9)(10)(11). More challenging electron-neutral substrates as well as the ones equipped with electron-donating groups, which are elusive in some redox-based approaches, reacted well delivering the desired 2-aryl-pyrroles in good yields (11, 13 and 5).…”

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

“…The pair of radical ions escapes the solvent cage by diffusion to give radical ions, which could initiate chemical reactions or reverse electron transfer ( Scheme 1 ) [ 6 ]. The continuously increasing demand for sustainable synthesis has encouraged chemists to pursue more efficient methods to manufacture fine and usable chemicals [ 7 ]. The reactions that EDA complexes participate in have been shown to be an enormous success, mainly due to the fact that they obviate photoredox catalysts or transition metal catalysts in the vast majority cases.…”

Harnessing Radical Chemistry via Electrochemical Transition Metal Catalysis

“…The capacity of carboxylic acids to act as an adaptive functionality renders them ideal starting materials in organic synthesis ( Hu et al., 2020 ). In this context, redox-active esters from readily available alkyl carboxylic acids have been recently recognized as versatile alkyl halide surrogates for applications in metal-catalyzed cross-coupling reactions ( Murarka, 2018 ).…”