Direct Catalytic Addition of Alkylnitriles to Aldehydes by Transition-Metal/NHC Complexes

Direct catalytic addition of alkylnitriles to aldehydes allows for an atom-economical access to b-hydroxynitriles under proton transfer conditions. Direct use of alkylnitriles as pronucleophiles has been hampered due to their low acidity resulting in an inability to generate acyano carbanions in a catalytic manner. A transition metal/ N-heterocyclic carbene (NHC) complex prepared from [{Rh(OMe)(cod)}(2)] and an imidazolium-based carbene was identified as an effective catalyst to promote the reaction with as little as 1.25 mol% of catalyst loading. The corresponding Rh complex, derived from chiral triazolium salt, rendered the reaction enantioselective, albeit with moderate enantioselectivity.