(Invited) Electrocatalytic Radical-Polar Crossover Hydrofunctionalization of Alkenes

Abstract

Due to the unique reactivity of open-shell intermediates, the development of catalytic transformations driven by single-electron transfer (SET) has been an area of intense research in organic chemistry. In particular, the employment of unconventional means of activation, including photoredox catalysis and electrocatalysis, has provided unique entry to single-electron reactivities and led to new solutions to challenging synthetic problems that are not readily addressed using existing tools.We disclose a general electrocatalytic hydrofunctionalization by utilizing a wide range of alkenes. The integration of the two involves an electrochemically instigated cobalt-hydride-catalyzed radical-polar crossover of alkenes that enable the generation of key cationic intermediates, which could readily be entrapped by challenging nucleophiles. We highlight the importance of precise control of the reaction potential by electrochemistry in conjunction with the decisive role of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as the co-solvent to obtain optimal and exclusive chemoselectivity.In addition, we develope an electrocatalytic method for intramolecular hydroamination of allylic sulfonamides to access azetidines. The merger of cobalt catalysis and electricity enables regioselective generation of key carbocationic intermediates, which could directly undergo intramolecular C-N bond formation. The mechanistic investigations including electrochemical kinetic analysis suggest that the catalyst regeneration by nucleophilic cyclization is involved in the rate-determining step (RDS) of our electrochemical protocol and highlight the ability of electrochemistry in providing ideal means to mediate catalyst oxidation.