Chemo- and Regioselective Sequential Addition/[2,3]-Sigmatropic Rearrangement Reaction of Vinylsulfonium Salts with <i>N</i>-Heterocycles: Access to Functionalized Benzylic Thioethers

An efficient base-mediated sequential Michael addition/[2,3]-sigmatropic rearrangement between vinylsulfonium salts and <i>N</i>-nucleophiles has been developed, leading to a series of functionalized benzylic thioethers in 52-95% yields with high chemoselectivity, regioselectivity, and atom economy. The protocol enables mild conditions, is easy to manipulate, and exhibits a wide substrate range with good functional group tolerance. The viability of the method is also illustrated by gram-scale synthesis and further modification of target products and drug molecules, making it a valuable tool for drug discovery. A mechanistic rationale is further supported by deuterium-labeling experiments.