N-heterocyclic carbene (NHC) ligands with naphthyl side chains were employed for the synthesis of unsaturated, yet isolable [(NHC)Ir(cod)](+) (cod=1,5-cyclooctadiene) complexes. These compounds are stabilised by an interaction of the aromatic wingtip that leads to a sideways tilt of the NHC-Ir bond. Detailed studies show how the tilting of such N-heterocyclic carbenes affects the electronic shielding properties of the carbene carbon atom and how this is reflected by significant upfield shifts in the (CNMR)-C-13 signals. When employed in the intramolecular hydroamination, these [(NHC)Ir(cod)](+) species show very high catalytic activity under mild reaction conditions. An enantiopure version of the catalyst system produces pyrrolidines with excellent enantioselectivities.
Unusual NHC-Iridium(I) Complexes and Their Use in the Intramolecular Hydroamination of Unactivated Aminoalkenes
Falivene, Laura;Cavallo, Luigi;
2016
Abstract
N-heterocyclic carbene (NHC) ligands with naphthyl side chains were employed for the synthesis of unsaturated, yet isolable [(NHC)Ir(cod)](+) (cod=1,5-cyclooctadiene) complexes. These compounds are stabilised by an interaction of the aromatic wingtip that leads to a sideways tilt of the NHC-Ir bond. Detailed studies show how the tilting of such N-heterocyclic carbenes affects the electronic shielding properties of the carbene carbon atom and how this is reflected by significant upfield shifts in the (CNMR)-C-13 signals. When employed in the intramolecular hydroamination, these [(NHC)Ir(cod)](+) species show very high catalytic activity under mild reaction conditions. An enantiopure version of the catalyst system produces pyrrolidines with excellent enantioselectivities.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
