Novel Synthetic Routes to Complex Amines: the Catalytic Hydroamination of Alkynes and Hydroimination of Allenes

Abstract

Amines are valuable targets for synthesis in contexts of both research and industrial applications. This work proposes two atom-economical methods—hydroamination (HAM) and hydroimination (HIM)—as C-N bond formation strategies. A nickel-(N-heterocyclic carbene) catalyst system was developed to carry out HAM of internal, unactivated alkynes with aryl amines and cyclic secondary amines. It was demonstrated that the Ni-NHC catalyst was capable of promoting both HAM at room temperature and transfer hydrogenation to produce α-branched aryl amines. These two procedures were performed by the same catalyst to demonstrate an elegant 1-pot, multi-transformation protocol. Separately, optimization of a Rh-HIM catalyst system for the combination of monosubstituted allenes and aromatic N-H-ketimine was carried out to favor high conversion of substrates to the linear HIM product rather than [3+2] annulation. Both HAM and HIM C-N bond formation methods were found to be successful and capable of good conversion and selectivity for their respective products.