Copper(i)-catalysed transfer hydrogenations with ammonia borane.

Highly Z-selective alkyne transfer semihydrogenations and conjugate transfer hydrogenations of enoates can be effected by employing a readily available and air-stable copper(i)/N-heterocyclic carbene (NHC) complex, [IPrCuOH]. As an easy to handle and potentially recyclable H2 source, ammonia borane (H3NBH3) is used.