Heterocyclic thiolates and phosphine ligands in copper-catalyzed synthesis of propargylamines in water

The product obtained by reaction of deprotonation of 2-mercaptobenzothiazole or methimazole (2-mercapto-1-methylimidazole) with copper iodide in the presence of tertiary phosphines, PR2R' (R = R' = cyclohexyl; R = R' = phenyl; R = phenyl, R' = methyl) showed high catalytic activity in A3 coupling of a series of aldehydes with phenylacetylene and piperidine, yielding propargylamines. An investigation into the nature of active species carried out mainly by electrospray ionization mass spectrometry (ESI-MS) techniques underscores a crucial role played by organosulfur and organophosphorus compounds in the generation of active species responsible for these reactions. The coupling reactions were successfully carried out at low catalyst loadings in water/THF (20:1) and in relatively short reaction times. The scope of the reaction was also investigated with 20 examples.