Abstract
The dehydrogenative aryl C-H/N-H cross-coupling is a powerful synthetic methodology to install nitrogen functionalities into aromatic compounds. Herein, we report an electrochemical oxidation induced intermolecular cross-coupling between aromatics and sulfonimides with high regioselectivity through N-radical addition pathway under external-oxidant-free and catalyst-free conditions. A wide variety of arenes, heteroarenes, alkenes and sulfonimides are applicable scaffolds in this transformation. In addition, aryl sulfonamides or amines (aniline derivatives) can be obtained through different deprotection process. The cyclic voltammetry mechanistic study indicates that the N-centered imidyl radicals are generated via proton-coupled electron transfer event jointly mediated by tetrabutylammonium acetate and anode oxidation process.
Highlights
The dehydrogenative aryl C-H/N-H cross-coupling is a powerful synthetic methodology to install nitrogen functionalities into aromatic compounds
Compared with the well-established Buchwald−Hartwig and Ullmann amination[2,3,4,5,6,7,8], the direct amination of aryl C–H bonds, especially the dehydrogenative aryl C–H/N–H cross-coupling, represents a more straightforward and atom-economical strategy to access these essential molecules, which can circumvent the prefunctionalization of the aromatic substrates[9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24]
Anode oxidation has been proved as a convenient approach to generate N-centered radicals by cleavage of the strong N–H bonds from N–H precursors[66]
Summary
The dehydrogenative aryl C-H/N-H cross-coupling is a powerful synthetic methodology to install nitrogen functionalities into aromatic compounds. In this context, developing an efficient method to generate N-centered radicals from N–H reagent under external oxidant-free and catalyst-free conditions to realize dehydrogenative aryl C–H/N–H cross-coupling would be significantly appealing. The cross-coupling product 3aa can be afforded in acetonitrile with a 43% isolated yield by using a carbon rod anode and a platinum plate cathode in an undivided cell under 10 mA constant current for 4 h at ambient temperature (Table 1, Entry 2).
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