Synthesis of a Better N-Heterocyclic Carbene Ligand Yordanos Goshu, Christopher Hansen, Dr. Steven Baldwin, Professor Gregory Hillhouse

University of Chicago Collegiate Scholars ProgramGordon Center for Integrative Science, Department of Chemistry

University of Chicago, Illinois 60637

Synthetic Reaction

BackgroundAbstract

A new bulky N-heterocyclic carbene ligand, ITol*, was prepared through a 5 step synthesis with 82% overall yield, ending with the deprotonation of ITol*HCl by potassium t-butoxide. The ITol* ligand is being investigated on the basis of forming transition metal complexes by reacting it with PdCl2(SMe2)2 , which may permit its potential applications as a catalyst.

Representative NMR’s

Synthetic protocols for each step proved to be successful. The initial goal to improve the NMR spectra and increase solubility were accomplished, and the NMR spectra has revealed that ITol* salt has been successfully deprotonated and used to form a palladium compound , whose characterization and reactivity evaluation are underway.

N-heterocyclic carbenes (NHC) are known for acting as ligands for transition metal catalysts. A related NHC IPr* has been successful in stabilizing reactive low coordinate nickel complexes such as (IPr*)Ni=N(dmp).

(IPr*)Ni=N(dmp) (ref 2)

PurposeIPr* has some undesirable properties including its low solubility and complicated NMR spectra. The strategy behind the synthesis of ITol* is to replace the flanking phenyl groups with flanking p-tolyl groups to increase solubility and simplify the NMR spectra.

Conclusion

(1) Li, H; Zhu, R; Shi, W; He, K; Shi, Z. Org. Lett. 2012, 14, 4850.(2) DMP Imido Complex: Laskowski & Hillhouse JACS 2011, 133, 771

Reference

IPr*

ITol*