Challenge: The efficiency of olefin metathesis catalysts is often compromised by certain functional groups that may be present in the substrate, solvent or in trace reaction impurities. For example, Lewis bases can coordinate to the metal center of the active catalytic species, trigger its decomposition, or form a chelating ligand, reducing catalyst turn-over number. A common means to overcome such interference is to increase catalyst loading. However, while this seemingly obvious strategy might work for a one-off, small scale reaction, it is an unsustainably expensive solution for larger scale and decidedly not compatible with commercial processes.
Apeiron’s Solution: Choose the right catalyst and reaction conditions for the job – reduce catalyst loading and boost reaction yield and cost efficiency. Bulkier ligands shield the ruthenium metal center from unproductive coordination, effectively stabilizing the catalyst in the presence of otherwise troublesome functional groups. In the conversion of A to B illustrated below, nitro-Grela (AS2032), our workhorse catalyst for uncomplicated RCM conversions, was replaced with nitro-Grela-SiPr (AS2033). This simple change affords the desired product in comparable yield, but with 50 times lower catalyst loading and more than 5 times higher concentration.
Increased size of NHC ligand results in higher functional group tolerance and greater stability of the catalyst.