Abstract
Compounds bearing mono- and dibromomethyl groups are extensively utilized in synthetic
and medicinal chemistry. In this regard, selective debromination of readily or easily
accessible tribromomethyl compounds offers a direct and efficient method to access
those two moieties. In this work, we introduced Lewis base–borane-mediated selective
hydrodebromination of tribromomethyl groups via ionic or radical pathway. Using 4-(dimethylamino)pyridine–borane
(DMAP-BH3) as a hydride donor, monohydrodebromination of tribromomethyl groups was achieved
via nucleophilic substitution by hydride, delivering dibromomethyl groups. On the
other hand, treatment of tribromomethyl compounds with an N-heterocyclic carbene–borane
(NHC-BH2CN) as a boryl radical precursor in the presence of dilauroyl peroxide (DLP) as radical
initiator afforded monobromomethyl compounds through consecutive bromine atom abstractions
to cleave two C–Br bonds. Various tribromomethyl group bearing acetamides and acetates
were applied in this developed protocol, showcasing good functional group tolerance
and broad substrate scope.
Keyword
Lewis base–borane - boryl radical - selective debromination - halogen atom transfer
- hydride donor
