Sulfilimines are valuable tetravalent sulfur-nitrogen compounds with broad applications in synthetic chemistry, medicinal chemistry, and sulfur-containing functional molecules. Although sulfenamides have emerged as useful and readily accessible S(II) synthons for sulfur functionalization, most related transformations are still conducted under conventional solution-phase conditions, often with considerable solvent use, longer reaction times, and additional purification burden. Herein, we report an NFSI-promoted mechanochemical oxidative coupling of sulfenamides with phenols and related electron-rich aromatic partners for the rapid synthesis of sulfilimines. In a typical procedure, a sulfenamide substrate (1.0 equiv.), an aromatic coupling partner (1.2 equiv.), and NFSI (1.2 equiv.) were charged into a stainless-steel milling jar and subjected to ball milling at 450 rpm under solvent-free and additive-free conditions. The milling program consisted of forward rotation for 5 min, a 2 min pause, and reverse rotation for 5 min, and this sequence was repeated twice to give a total effective milling time of 20 min. Under the optimized conditions, sulfenamides bearing diverse sulfur-side substituents and N-acyl groups were converted into the corresponding sulfilimines in generally good yields. The aromatic coupling partner scope covered substituted phenols, naphthol, indole, and 1,3,5-trimethoxybenzene, indicating that the reaction is applicable to different electron-rich aromatic systems. A representative 3 mmol-scale experiment afforded the desired product without flash column chromatography, and a modified scale-up protocol using 1.2 equiv. of NFSI, 2-MeTHF as a liquid-assisted grinding additive, and prolonged milling improved the yield to 82%. The resulting sulfilimines could be further derivatized through O- or N-alkylation, and selected alkylated products underwent subsequent sulfur-center oxidation. Preliminary radical-trapping and solvent-free stirring control experiments suggested that a radical-chain-dominated pathway is unlikely and that ball milling promotes the reaction beyond simple thermal activation. Comparisons with representative solution-phase procedures and green-metrics analysis revealed clear reaction-stage advantages in reaction time, solvent intensity, and material efficiency. This method provides a concise mechanochemical approach to sulfilimines from readily available sulfenamides.

Key words: Mechanochemistry, Sulfenamides, Sulfilimines, Oxidative coupling, Solvent-free synthesis