Catalysis by electrons and holes: formal potential scales and preparative organic electrochemistry

Abstract

The present review surveys current chemical understanding of catalysis by addition and removal of an electron. As an overarching theme of this type of catalysis, we introduce the role of redox scales in oxidation and reduction reactions as a direct analogue of pK a scales in acid/base catalysis. Each scale is helpful in determining the type of reactivity to be expected. In addition, we describe several means of generating electrons and holes via chemical reactions, plasmonic resonance, radiolytic, photochemical and electrochemical methods. We specifically draw parallels between the now well-established fields of photoredox catalysis and chemical opportunities made available by electrochemical methods. We highlight accessible potential ranges for a series of electrochemical solvents and provide a discussion on experimental design, pitfalls and some remaining challenges in preparative organic electrochemistry.

Organic reactions for the electrochemical and photochemical production of chemical fuels from CO2 – The reduction chemistry of carboxylic acids and derivatives as bent CO2 surrogates

“…From an organic chemistry perspective, the solar fuels field may contribute a wealth of knowledge regarding the electrochemical generation of selective and functional-group tolerant reducing agents. As such, efforts in the electrochemical conversions of CO 2 to chemical fuels may provide mild conditions for transformations related to carboxylic acids and intermediates [131]. CO 2 capture and subsequent reduction chemistry has unfortunately not yet been fully elucidated in terms of electrochemical regimes and we remain mindful of coupled chemical processes related to the chemical reactivity of possible intermediates in the kinetic timescale of electrolytic preparative experiments.…”

“…The electrochemical method was attractive in that it had a good functional group tolerance: tolerating carboxylic acids, nitriles, olefins and epoxide functionality. Unfortunately electrolytic methods have not yet been adopted as a mainstream tool of organic synthesis and we remain forward-looking to developments in the field [131].…”

Synthetic Organic Electrochemical Methods Since 2000: On the Verge of a Renaissance

“…Electrochemical potentials of common organic functional groups have been summarized elsewhere and will not be reiterated. 50,51 It is hoped that this color coded and annotated format will aid the reader to rapidly identify classes of reactions and setups without needing to refer to the text.…”

External oxidant-free cross-coupling: electrochemically induced aromatic C–H phosphonation of azoles with dialkyl-H-phosphonates under silver catalysis

“…Thus, new electrochemical reactions of the C(sp 2 )-H phosphorylation [20][21][22][23][24][25][26][27] have been proposed in recent years. The progress of electroorganic synthesis in this field is described in numerous reviews 22,23,[28][29][30][31][32] and papers concerning some recent advances in C-H functionalization, such as fluoroalkylation, [33][34][35][36][37][38] amination, [39][40][41][42] aziridination, 43 oxygenation, [44][45][46] arylation, 47 alkylation, 48 amino-oxygenation, 49 etc. The first electrochemical oxidative phosphorylation of benzoxazoles in the presence of a 3d metal catalyst was reported in 2016.…”