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Large-Scale Synthesis of a Niche Olefin Metathesis Catalyst Bearing an Unsymmetrical N-Heterocyclic Carbene (NHC) Ligand and its Application in a Green Pharmaceutical Context |
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| Authors: | Tomasz Nienałtowski Paweł Szczepanik Paweł Małecki Dr Dorota Czajkowska-Szczykowska Dr Stefan Czarnocki Dr Jolanta Pawłowska Dr Anna Kajetanowicz Prof Karol Grela |
| Institution: | 1. Biological and Chemical Research Centre, Faculty of Chemistry, University of Warsaw, Żwirki i Wigury 101, 02-089 Warsaw, Poland
Polpharma SA Pharmaceutical Works, Pelplinska 19, 83-200 Starogard Gdanski, Poland These authors contributed equally to this work.;2. Biological and Chemical Research Centre, Faculty of Chemistry, University of Warsaw, Żwirki i Wigury 101, 02-089 Warsaw, Poland These authors contributed equally to this work.;3. Biological and Chemical Research Centre, Faculty of Chemistry, University of Warsaw, Żwirki i Wigury 101, 02-089 Warsaw, Poland;4. Apeiron Synthesis SA, Duńska 9, 54–427 Wrocław, Poland;5. Polpharma SA Pharmaceutical Works, Pelplinska 19, 83-200 Starogard Gdanski, Poland |
| Abstract: | A large-scale synthesis of known Ru olefin metathesis catalyst VII featuring an unsymmetrical N-heterocyclic carbene (NHC) ligand with one 2,5-diisopropylphenyl (DIPP) and one thiophenylmethylene N-substituent is reported. The optimised procedure does not require column chromatography in any step and allows for preparation of up to 0.5 kg batches of the catalyst from simple precursors. The application profile of the obtained catalyst was studied in environmentally friendly dimethyl carbonate (DMC). Although VII exhibited low efficiency in cross-metathesis (CM) with electron-deficient partners, good to excellent results were noted for substrates featuring easy to isomerise C−C double bonds. This includes polyfunctional substrates of medicinal chemistry interest, such as analogues of psychoactive 5F-PB-22 and NM-2201 and two PDE5 inhibitors—Sildenafil and Vardenafil. Finally, a larger scale ring-closing metathesis (RCM) of a Vardenafil derivative was conducted in DMC, allowing for straightforward isolation of the expected product (23 g) in high yield and with low Ru contamination level (7.7 ppm). |
| Keywords: | large-scale synthesis medicinal chemistry N-heterocyclic carbene (NHC) ligands olefin metathesis ruthenium catalysts |