Highly Chemoselective Synthesis of α, α-Dideuterio Amines by the Reductive Deuteration of Thioamides Using Mild SmI 2 -D 2 O

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