Catalyst‐ and Reagent‐Free Electrochemical Azole C−H Amination

Abstract

Catalyst- and chemical oxidant-free electrochemical azole C-H aminations were accomplished via cross-dehydrogenative C-H/N-H functionalization. The catalyst-free electrochemical C-H amination proved feasible on azoles with high levels of efficacy and selectivity, avoiding the use of stoichiometric oxidants under ambient conditions. Likewise, the C(sp )-H nitrogenation proved viable under otherwise identical conditions. The dehydrogenative C-H amination featured ample scope, including cyclic and acyclic aliphatic amines as well as anilines, and employed sustainable electricity as the sole oxidant.

Electrochemical Dehydrogenative Cross‐Coupling of Quinoxalin‐2(1H)‐ones with Amines for the Synthesis of 3‐Aminoquinoxalinones

“…As for the reaction mechanism of the oxidative amination of quinoxaline‐2(1 H )‐ones, both a nucleophilic addition (ionic mechanism) and a radical pathway are reported in literatures . Therefore, it is safe to assume that our electrochemical version may also proceed through ionic or radical pathways.…”

“…Moreover, the oxidation potential of the mixture of 1 a with 2 a is approximately 0.7 V lower than the oxidation potential of amine 2 a , which indicates direct radical transfer in the process. Based on these results and related literature, we suggest that the electrochemical oxidative amination might involves a radical process, although more evidence is required.…”

Electrochemical C−H Amidation of Heteroarenes with N‐Alkyl Sulfonamides in Aqueous Medium

“…Thus, the development of efficient and more environmentally friendly synthetic methods is still highly desirable and valuable, [9d] particularly by means of electrosynthesis. In connection with our continued interest in electrochemical syntheses [14, 15] and C−N bond formation using electricity as the sole oxidant, [16] we questioned whether the efficiency and mildness noted in the N ‐radical formation could be translated into an electro‐oxidative heteroarene amidation strategy. We have now devised an unprecedented C−H amidation of heteroarenes that can be performed with commercially available, inexpensive reagents under green and operationally‐simple electrochemical conditions (Scheme 1 c).…”

“…[13] At the beginningo ft his reaction, stoichiometric NaClO is needed to oxidatively quencht he iridium III catalystt og enerate iridium IV .T hus, the development of efficient and more environmentally friendly synthetic methods is still highly desirable and valuable, [9d] particularly by meanso fe lectrosynthesis. In connection with our continued interesti ne lectrochemical syntheses [14,15] and CÀNb ond formation using electricity as the sole oxidant, [16] we questioned whether the efficiency and mildness noted in the N-radical formation could be translated into an electro-oxidative heteroarenea midation strategy.W eh ave now devised an unprecedented CÀHa midation of heteroarenes that can be performed with commercially available, inexpensive reagents under green and operationally-simplee lectrochemical conditions (Scheme 1c). Compared to previously disclosedm ethods, salient features of our strategy comprise (a) the absence of externalc hemical oxidants, (b) (photo)redox and metal catalyst-free condition, (c) the use of au ser-friendly undividedc ell setup without additional electrolyte, (d)high regioselectivity,and (e) full water tolerance.…”

Electrochemical/Photochemical Aminations Based on Oxidative Cross-Coupling between C–H and N–H

“…Very recently, the same reaction was also accomplished through direct electrolysis by the Ackermann group (Scheme 15). 24…”