Abstract:
Salen ligands and their corresponding complexes are well known in the field of asymmetric catalysis due to their success in stereoselective reactions. A method that easily allows for recycling of the catalyst without degradation of catalytic activity would make them more industrially viable. The generation of a Task Specific Ionic Liquid (TSIL) by attaching tributylphosphonium moieties to Jacobsen’s ligand could promote the entrainment of the catalyst in an ionic liquid (IL). This would potentially create a recyclable system where the desired product can be extracted, leaving the IL/catalyst layer behind ready for reuse. The racemic and asymmetric versions of the ligand, 5,5'-(1E,1'E)-(cyclohexane-1,2-diylbis(azan-1-yl-1-ylidene))bis(methan-1-yl-1-ylidene)bis(3-tert-butyl-4-hydroxy-5,1-phenylene)bis(methylene)bis(tributylphosphonium) hexafluoridophosphate, as well as their respective copper complexes were successfully synthesized and characterized. These were applied to aziridinations of styrene, using tosyliminophenyliodinane (PhINTs) as a nitrene source, in both acetonitrile and three different ILs. Acetonitrile generated yields of up to 88%, however no product was extracted from 1-butyl-3-methylimidazolium hexafluoridophosphate, tetradecyl(trihexyl) phosphonium hexafluoridophosphate and chloride.