Sulfonamides as N-Centered Radical Precursors for C-N Coupling Reactions To Generate Amidines

By: Deng, Guogang ; Chen, Zhuo ; Bai, Yifeng ; Zhang, Lening ; Xia, Dazhen ; Duan, Shengzu ; Chen, Wen ; Zhang, Hongbin ; Walsh, Patrick J. ; Yang, Xiaodong

Organic Letters

DOI：https://doi.org/10.1021/acs.orglett.4c01014

Published：2024-04-30

Abstract

Nitrogen-centered radicals (NCRs) are valuable intermediates for the construction of C-N bonds. Traditional methods for the generation of NCRs employ toxic radical initiators, transition metal catalysts, photocatalysts, or organometallic reagents. Herein, we report a novel strategy for the generation of NCRs toward the construction of C-N bonds under transition-metal-free conditions. Thus, super-electron-donor (SED) 2-azaallyl anions undergo single-electron transfer (SET) with sulfonamides, forming aminyl radicals (R2N center dot, R = alkyl) and culminating in the generation of amidines bearing various functional groups (33 examples, up to 96% yield). Broad substrate scope and gram-scale telescoped preparation demonstrate the practicality of this method. Radical clock and electron paramagnetic resonance (EPR) experiments support the proposed radical coupling pathway between the generated N-centered radical and the C-centered 2-azaallyl radical.