Marek Klučiar

First ruthenium catalyst containing alkylazolium tag
covalently connected to N-heterocyclic carbene ligand

Marek Klučiar, UW
Supervisor: prof. Karol Grela (UW)

Since its discovery, olefin metathesis became a very powerful tool in synthetic organic chemistry. Especially ruthenium homogenous Grubbs 1a,b and Hoveyda–Grubbs 2a,b type catalysts offer many advantages. On the other hand, ruthenium catalyzed metathesis reaction share common liability of all transition metal-catalysed reactions, which is difficult separation of toxic metal residues. To solve this issue various removal protocols were proposed but with moderate efficiency and ruthenium content in 100 – 1200 ppm. As olefin metathesis reaction is used in pharmaceutical processes and production of fine chemicals, ruthenium content must be drastically decreased. To achieve this, various concepts of recovery and recycling have been proposed. Notably, catalysts were immobilized on different support and various polar or non-polar tags were introduced on dissociating phosphine, pyridine or alkylidene ligands ^[1]. Therefore tag introduction to the non-dissociative N-heterocyclic carbene ligand (NHC)^[2] in second generation of Hoveyda type catalysts 2b should allow enhanced separation and recycling properties of metathesis catalyst. Until now NHC ligands were less studied as only few examples of functionalization of this ligand are known. Introduction of alkylazolium tag on NHC is not known and promises environmentally friendly metathesis process with low ruthenium contamination and enhanced catalyst recycling. In continuation of our program to develop a ‘green’ metathesis catalyst, herein we report the FIRST stable ruthenium homogeneous catalyst containing alkylazolium tag covalently connected to N-heterocyclic carbene ligand.

Chairman - dr hab. Andrzej Kudelski (UW)

Discussion