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Unusual NHC–Iridium(I) Complexes and Their Use in the Intramolecular Hydroamination of Unactivated Aminoalkenes
Author(s) -
Sipos Gellért,
Ou Arnold,
Skelton Brian W.,
Falivene Laura,
Cavallo Luigi,
Dorta Reto
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201600378
Subject(s) - hydroamination , intramolecular force , enantiopure drug , carbene , iridium , chemistry , catalysis , medicinal chemistry , cyclooctadiene , photochemistry , stereochemistry , enantioselective synthesis , organic chemistry
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 13 C NMR 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.