Rapid and chemoselective imidation of sulfides in aqueous buffer enabled by a novel guanidine-derived N-O reagent

Herein we report the facile synthesis of a series of novel N-O reagents and identify N′-di-Boc-N″-[(mesitylsulfonyl)oxy]-guanidine as an efficient imidating reagent. This reagent is synthetically scalable and bench-stable, yet it shows unprecedented reactivity and chemoselectivity towards S(II) in buffer/hexafluoroisopropanol (HFIP) system, to generate a new class of N-guanyl sulfilimines. Further transformation of N-guanyl sulfilimines to N-guanyl sulfoximines provides us a chance to investigate these rarely reached compounds, which are shown to be versatile precursors to a variety of N-heterocyclic and NH-sulfoximines. Our work provides an addition to the tool box of both sulfur imidation and guanidine synthesis, especially for the need of rapid and selective modifications of sulfur(II) center under biocompatible conditions.