Electroredox carbene organocatalysis with iodide as promoter

Abstract

Oxidative carbene organocatalysis, inspired from Vitamin B1 catalyzed oxidative activation from pyruvate to acetyl coenzyme A, have been developed as a versatile synthetic method. To date, the α-, β-, γ-, δ- and carbonyl carbons of (unsaturated)aldehydes have been successfully activated via oxidative N-heterocyclic carbene (NHC) organocatalysis. In comparison with chemical redox or photoredox methods, electroredox methods, although widely used in mechanistic study, were much less developed in NHC catalyzed organic synthesis. Herein, an iodide promoted electroredox NHC organocatalysis system was developed. This system provided general solutions for electrochemical single-electron-transfer (SET) oxidation of Breslow intermediate towards versatile transformations. Radical clock experiment and cyclic voltammetry results suggested an anodic radical coupling pathway.

Migration from Photochemistry to Electrochemistry for [2 + 2] Cycloaddition Reaction

“…First was the reduction peak of water near −0.98 V vs Ag/AgCl, and the second one was attributed to the reduction of chalcone 1a to its radical anion species near −1.35 V vs Ag/AgCl. As shown in the oxidation part of the CVs, the oxidation peaks of iodide take shape in the absence of chalcone, but the oxidation peaks of iodide were absent in the presence of chalcone, while two new peaks emerged. This observation can be explained in terms of consumption of electro-generated iodine and replacing the used iodide.…”

Synergistic Visible Light Photocatalysis with Organocatalysis

“…Organocatalytic reactions have the advantages of mild reaction conditions, uncomplicated operation, and a wide range of catalysts to be used, [4] however, organocatalysts still have the disadvantages, such as lower catalytic efficiency, larger catalyst loading compared with metal catalysts. In recent years, attention has been paid to combining organocatalysis with other catalytic modes such as: photoredox, [5] electrocatalysis, [6] metal catalysis [7] . Such approaches widen the realm of organocatalysis and further expand its synthetic potential.…”

Electricity-driven asymmetric bromocyclization enabled by chiral phosphate anion phase-transfer catalysis

“…However, their applicability in electrochemistry varied significantly [19][20][21][22][23][24][25] . Among them, covalent bonding with a chiral catalyst proved most successful [26][27][28][29][30][31][32] . For example, chiral amine catalysis via an enamine intermediate has been established in many electrochemical processes, in which the covalently linked substratecatalyst adduct ensures robust asymmetric induction in the presence of many other interactions in a complex electrochemical system.…”