Highly Chemoselective\nSynthesis of α, α‑Dideuterio\nAmines by the Reductive Deuteration of Thioamides Using Mild SmI<sub>2</sub>–D<sub>2</sub>O

An efficient and chemoselective protocol for the single-electron-transfer\n(SET) reductive deuteration of thioamides using SmI<sub>2</sub> and\nD<sub>2</sub>O is reported. This method uniquely produces α,α-dideuterio\namines via a thio-ketyl radical intermediate without generating alcohol\nbyproducts, distinguishing it from the SET reduction of amides. The\ninherent high reactivity of thioamides obviates the need for ligands\nlike Et<sub>3</sub>N to improve the reducing power of SmI<sub>2</sub>, thereby enabling milder reaction conditions that are compatible\nwith a broad range of sensitive functional groups. This protocol tolerates\nboth primary and secondary aliphatic and aromatic thioamides, leading\nto the synthesis of 27 α,α-dideuterio amines and valuable\ndeuterated nitrogen heterocycles with >95% deuterium incorporations.