NHC-Gold(I) complexes active in phenylacetylene hydroamination

Imines are key molecules for the synthesis of several N-containing compounds of industrial interest. The hydroamination reaction represents an excellent green strategy to build C-N bonds by adding amines to multiple carbon bonds with a 100% atom economy. The addition of amines to double and triple carbon bonds requires very high activation barriers, but transition metal complexes can be used to activate multiple C-C bonds.1 Recently, NHC-gold complexes were shown to be able to promote hydroamination of alkynes.2 Herein we present highly regioselective Markovnikov hydroaminations of phenylacetylene with arylamines in the presence of different N-Heterocyclic gold(I) complexes (Figure 1). The best reaction conditions were identified by screening co-catalysts and solvents. Among the tested catalysts, the most active, in the model hydroamination of phenylacetylene with aniline, was tested in the hydroamination of phenylacetylene with a large variety of amines. Relying on previous mechanistic studies,3 DFT (Density Functional Theory) studies were conducted to rationalized the dramatical yield difference observed by varying the activating/deactivating magnitude of the aryl substituents.