CH Functionalization via Chalcogen and Pnictogen Salts

Abstract CH functionalization is an enabling technology for medicinal chemistry efforts, allowing a greater chemical landscape to be assayed in a shorter time frame from non‐pre‐functionalized materials. Part of an elite class of the so‐called late‐stage functionalization (LSF) reactions, CH functionalization can take many forms, with one emerging form involving the intermediacy of chalcogen and pnictogen salts. Although canonical boronate esters or halides are the “go‐to” species for CH functionalization, three unrelated cationic groups (phosphonium, pyridinium, and thianthrenium) have emerged as viable alternatives with rich avenues for diversification. Despite being a two‐step process to achieve the net desired CH transformation, the ease of entry and the unusual regiochemical selectivity of salt formation make these chalcogen and pnictogen indispensable assets to LSF efforts. This article details the fundamentals of using these salts for CH functionalization, with an emphasis on how they can be enabling technologies for medicinal chemistry.