Sammanfattning
Cyclometalated N-heterocyclic carbene (NHC)-NTs-AuCl2 complexes of type [(NHC)Au(N)Cl-2] are presented as a stable precatalyst, easily activated in situ by an acid (HX) for cationic [(NHC)AuCl2]X catalysis. The "ethyl-and propyl-tosylamide arm" tethered NHC-Au(III)Cl-3 complexes can be smoothly converted to cyclometalated (-HCl) analogues by K2CO3 treatment, and, via the addition of a stoichiometric amount of Br & oslash;nsted acid (HX), can be further converted to [NHC-Au(III)Cl-2]X carrying various counteranions (X = CCl3CO2-, CF3CO2-, MsO-, TsO-, BF4-, TfO-, and Tf2N-). We studied this concept in catalysis using the cycloisomerization of 2-alkynylphenol to benzofurans as a probe reaction. Excellent yields were obtained in 2 h with an equimolar 1 mol % loading of the Mes-NHC-propyl-NTs-AuCl2 precatalyst and MsOH as the acid additive under ambient conditions in CHCl3. The single crystal structure for a cyclometalated NHCAu(III)-complex was characterized by X-ray analysis. H-1 NMR monitoring of reaction kinetics suggests that the in situ formed Au(III) complex is the catalytically active species.
Originalspråk | engelska |
---|---|
Tidskrift | Organometallics |
Volym | 43 |
Nummer | 5 |
Sidor (från-till) | 605-610 |
Antal sidor | 6 |
ISSN | 0276-7333 |
DOI | |
Status | Publicerad - 21 feb. 2024 |
MoE-publikationstyp | A1 Tidskriftsartikel-refererad |
Vetenskapsgrenar
- 116 Kemi