N-heterocyclic carbenes (NHCs) have a wide range of applications, especially in transition-metal catalysis, due to their stability and the easy modification of their electronic and steric properties. Compared to the commonly used NHCs with five-membered rings, their six-membered counterparts have a wider N–C–N angle and higher basicity, which is interesting for catalytic applications.
A. Stephen K. Hashmi and colleagues, University of Heidelberg, Germany, have developed a synthesis strategy for such six-membered NHCs in the form of gold complexes (pictured). The team used gold isonitrile complexes and functionalized amines as building blocks, which allowed them to synthesize a wide range of six-membered NHC complexes. The reactants were combined at room temperature in the presence of the base triethylamine (NEt3) in dichloromethane (DCM) as a solvent, and the desired NHC complexes were obtained in good to excellent yields.
The method was suitable for the synthesis of unsymmetrically substituted saturated carbene complexes, but also for oxo-carbenes and partly unsaturated NHCs. These products have the potential to be functionalized further for specific applications.
- Synthesis of Different Classes of Six-Membered Gold(I) NHC Complexes by the Isonitrile Route,
Thomas Wurm, Florian Mulks, Constantin R. N. Böhling, Dominic Riedel, Poorya Zargaran, Matthias Rudolph, Frank Rominger, A. Stephen K. Hashmi,