Electroredox Carbene Organocatalysis with iodine cocatalyst

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 studied in NHC catalyzed organic synthesis. Herein, an electroredox NHC organocatalysis system with iodine cocatalyst was developed. With the help of non-uniform distribution of electrolysis system, NHC and iodine, which was normally not compatible in chemical reaction, cooperated well in the electrochemical system. This cocatalyst 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.

Visible-light Mediated Ring Opening Reaction of Alkylidenecyclopropanes for the Generation of Homopropargyl Radical

Classical cyclopropylcarbinyl radical clock reactions have been widely applied to conduct the mechanistic studies on probing radical process for a long time; however, alkylidenecyclopropanes, which have a similar molecular structure...

Evidence for a Radical Mechanism in Cu(II)-Promoted SnAP Reactions

Saturated nitrogen heterocycles can be found with increasing abundance in bioactive molecules despite a limited number of methods to access these scaffolds. However, the coupling of recently introduced SnAP [tin (Sn) amine protocol] reagents with a wide range of aldehydes and ketones has proven to be a reliable, practical, and versatile one-step approach to saturated N-heterocycles. While effective, the lack of mechanistic understanding limits efforts to develop new catalytic and enantioselective variants. To distinguish between a polar or radical mechanism, we assessed Lewis and Brønsted acids, radical trapping experiments, and radical clock SnAP reagents reinforcing the current understanding of the SnAP protocol as a radical cyclization.