Metal Complexes of Very Bulky N,N′‐Diarylimidazolylidene N‐Heterocyclic Carbene (NHC) Ligands with 2,4,6‐Cycloalkyl Substituents

Abstract

Abstract1,3,5‐Tricycloalkylbenzene (cycloalkyl = C5H9, C6H11) was converted into the respective anilines (by means of nitration and reduction) and then into the corresponding diimines (with glyoxal), the cyclization of which with (HCHO)n/ZnCl2 provided the respective 1,3‐bis(2,4,6‐tricyclopentylphenyl)imidazolium salt in modest yields. An analogous reaction sequence that employed acenaphthene‐1,2‐dione instead of glyoxal yielded the two azolium salts in good yields, which were converted into the respective N‐heterocyclic carbene (NHC) complexes [(NHC)AgCl], [(NHC)AuCl], [(NHC)RhCl(cod)] (cod = cyclooctadiene), and [(NHC)RhCl(CO)2].

Direct Synthesis of Ketones from Methyl Esters by Nickel‐Catalyzed Suzuki–Miyaura Coupling

“…Theuse of the 2,4,6-tricyclopentylaniline-derived N-heterocyclic carbine,which we refer to as IPr Cyp ,was found to be particularly important. [22] Monodentate (entry 2) and bidentate (entry 3) phosphines as well as the NHC ligand ICy (entry 4) gave no detectable product. While IPr Cyp is analogous to the more common ligands IPr and SIPr,t hese gave consistently lower yields (entries 5a nd 6).…”

Direct Synthesis of Ketones from Methyl Esters by Nickel‐Catalyzed Suzuki–Miyaura Coupling

“…Using aN ic atalyst, K 3 PO 4 as base,a nd toluene as solvent, the corresponding Suzuki-Miyaura ketone product 3 could be obtained in 80 %yield (Table 1entry 1 the 2,4,6-tricyclopentylaniline-derived N-heterocyclic carbine,which we refer to as IPr Cyp ,was found to be particularly important. [22] Monodentate (entry 2) and bidentate (entry 3) phosphines as well as the NHC ligand ICy (entry 4) gave no detectable product. While IPr Cyp is analogous to the more common ligands IPr and SIPr,t hese gave consistently lower yields (entries 5a nd 6).…”

Synthesis of an ortho‐Methyl‐N,N′‐bis(triptycenyl) N‐Heterocyclic Carbene Ligand and Its Metal Complexes

“…Following the removal of the Boc group, aniline 5 was treated with oxalyl chloride to provide diamide 6 , which was then reduced to the diamine 7 . The cyclization of 7 according to standard procedures gave imidazolinium salt 8· HCl, which is a very convenient precursor to numerous NHC–metal complexes . The azolinium salt 8· HCl occurs as two isomers with a syn and anti orientation of the two triptycene wings.…”

“…[5a] Grubbs–Hoveyda second‐generation complex [RuCl 2 (=CHC 6 H 4 O i Pr)( 8 )] was obtained from Grubbs–Hoveyda first‐generation complex and 8· HCl (Scheme ). [12b], …”