Efficient Rhodium-Catalyzed Multicomponent Reaction for the Synthesis of Novel Propargylamines

[{Rh(μ‐Cl)(H)2(IPr)}2] (IPr = 1,3‐bis‐(2,6‐diisopropylphenyl)imidazole‐2‐ylidene) was found to be an efficient catalyst for the synthesis of novel propargylamines by a one‐pot three‐component reaction between primary arylamines, aliphatic aldehydes, and triisopropylsilylacetylene. This methodology offers an efficient synthetic pathway for the preparation of secondary propargylamines derived from aliphatic aldehydes. The reactivity of [{Rh(μ‐Cl)(H)2(IPr)}2] with amines and aldehydes was studied, leading to the identification of complexes [RhCl(CO)IPr(MesNH2)] (MesNH2 = 2,4,6‐trimethylaniline) and [RhCl(CO)2IPr]. The latter shows a very low catalytic activity while the former brought about reaction rates similar to those obtained with [{Rh(μ‐Cl)(H)2(IPr)}2]. Besides, complex [RhCl(CO)IPr(MesNH2)] reacts with an excess of amine and aldehyde to give [RhCl(CO)IPr{MesNCHCH2CH(CH3)2}], which was postulated as the active species. A mechanism that clarifies the scarcely studied catalytic cycle of A3‐coupling reactions is proposed based on reactivity studies and DFT calculations. Mix ′em together! A range of new propargylamines have been prepared by a multicomponent reaction catalyzed by [{Rh(μ‐Cl)(H)2(IPr)}2] (IPr = 1,3‐bis‐(2,6‐diisopropylphenyl)imidazole‐2‐ylidene). This reaction utilises primary arylamines, aliphatic aldehydes, and triisopropylsilylacetylene as starting materials, because alternative synthetic methods are difficult to apply due to the instability of the corresponding imines. A catalytic cycle that sheds light on this scarcely studied mechanism is proposed based on theoretical calculations and experimental data.