Thiamine carbene liganded gold (I) chloride catalyses an efficient aldehyde-alkyne-amine coupling reaction in water

Propargylamines are versatile synthetic precursors that are widely used in the synthesis of pharmaceuticals and other bioactive molecules. One convenient method to access these molecules is metal-catalysed coupling of aldehyde, alkyne and amine (A³ coupling), which was first developed by Li and co-workers. Over the last two decades, this catalytic coupling reaction has been developed to use a diverse array of metal salts and organometallic complexes. As a result, it has been widely used in the synthesis of natural products and other bioactive compounds. Here we report the first time synthesis of a gold (I) catalyst using the water-soluble vitamin B1 or thiamine as an NHC ligand and its use as a catalyst of the A³ coupling. Remarkably, the resulting NHC-gold (I) catalyst is watersoluble, resistant to oxygen and highly efficient in the catalysis of the coupling reaction in open air, at low temperature and in water or under solvent-free conditions.