A combined experimental and computational study of ligand-controlled Chan-Lam coupling of sulfenamides
Kaiming Han, Hong Liu, Madeline E. Rotella, Zeyu Xu, Lizhi Tao, Shufeng Chen, Marisa C. Kozlowski, Tiezheng Jia
Abstract
Abstract The unique features of the sulfenamides’ S(II)-N bond lead to interesting stereochemical properties and significant industrial functions. Here we present a chemoselective Chan–Lam coupling of sulfenamides to prepare N -arylated sulfenamides. A tridentate pybox ligand governs the chemoselectivity favoring C–N bond formation, and overrides the competitive C-S bond formation by preventing the S,N-bis-chelation of sulfenamides to copper center. The Cu(II)-derived resting state of catalyst is captured by UV-Vis spectra and EPR technique, and the key intermediate is confirmed by the EPR isotope response using 15 N-labeled sulfenamide. A computational mechanistic study reveals that N -arylation is both kinetically and thermodynamically favorable, with deprotonation of the sulfenamide nitrogen atom occurring prior to reductive elimination. The origin of ligand-controlled chemoselectivity is explored, with the interaction between the pybox ligand and the sulfenamide substrate controlling the energy of the S -arylation and the corresponding product distribution, in agreement with the EPR studies and kinetic results.