Double A³‐Coupling of Primary Amines Catalysed by Gold Complexes

A novel family of dipropargylamines has been synthesised in one pot through a double catalytic A 3 ‐coupling of five components. Cationic [Au I ‐L][SbF 6 ] complexes (L=JohnPhos) are extremely active catalysts for the double A 3 ‐coupling of primary amines (aliphatic or aromatic), formaldehyde and trimethylsilylacetylene. Several reactions of LAu‐amine complexes with organic reagents were studied and followed by NMR and HRMS (ESI) analyses, providing information about the reaction mechanism. Specifically, the role of the π‐gold(I) acetylide complexes as active catalyst species was firmly confirmed. Most of the intermediates of this five‐component coupling were identified by GC‐MS spectrometry, lending support to the mechanistic proposal. In some cases, cationic amine‐gold(I)‐L complexes corresponding to the activated reagent or intermediate were isolated and characterised by single‐crystal X‐ray diffraction analysis, their spectroscopic properties were recorded, and their catalytic activity evaluated. Protic solvents influence the course of the reaction by effecting the double deprotection of dipropargylamines, providing a convenient route to dipropargylamines with double‐deprotected silyl moieties. When NaOH is present in the reaction media, formation of cationic acetylide‐dipropargylamine gold(I) and neutral hydroxide LAuOH complexes, respectively, as high and less active intermediate catalyst forms occur.