NHC-copper hydrides as chemoselective reducing agents: catalytic reduction of alkynes, alkyl triflates, and alkyl halides

The NHC-copper-catalyzed Z-selective semi-reduction of terminal and internal alkynes, as well as the NHC-copper-catalyzed reduction of primary alkyl triflates and primary and secondary alkyl iodides and bromides are described. The high chemoselectivity demonstrated in these examples illustrates the mild nature of copper hydride complexes as reducing agents, which have applications in synthetic chemistry beyond their traditional role in the reduction of activated alkenes and carbonyl compounds.