Insights into the formation of ruthenium hydrides via Fischer carbene intermediates Katie Grant and Guy Lloyd-Jones University of Edinburgh, UK Olefin metathesis is a key C-C bond formation reaction and is used in a variety of fields including natural product synthesis, fine chemical synthesis and API synthesis. 1 However, progress has been hampered in part due to unwanted side reactions such as isomerisation. 1 Research has shown the culprit for these side reactions is a ruthenium hydride species. 2 Once identified it was realised that if the formation of such a species could be controlled then there was scope for tandem catalytic reactions in which metathesis could be followed by isomerisation or hydrogenation. 3,4 This work focusses on elucidating the mechanism of one such synthesis developed by Nishida and co-workers. 5 In their work they developed a route based on a previously reported preparation by Grubbs and Louie in which a Grubbs metathesis catalyst was reacted with ethyl vinyl ether to form a Fischer-type carbene, 2 subsequently this was thermally decomposed to form the ruthenium hydride species of interest, RuHCl(CO)(L) 2 . Nishida’s methodology replaced the ethyl vinyl ether with vinyloxy trimethylsilane, allowing for lower reaction temperatures and greater selectivity for isomerisation. Using in situ 1 H NMR and kinetic modelling, reaction constants, key reaction parameters and intermediate species have been determined. 6 From these results a preliminary mechanism has been proposed. References 1. S. Higman, J.A.M. Lummiss, D.E. Fogg, Angew. Chem. Int. Ed ., 2016 , 55 , 3552-3565. 2. Louie, R. H. Grubbs, Organometallics, 2002 , 21 , 2153-2164. 3. E. Fogg, E. N. dos Santos, Coord. Chem. Rev. , 2004 , 248 , 2365-2379.
4. E. Sutton, B. A. Seigal, D. F. Finnegan, M. L. Snapper, J. Am. Chem. Soc., 2002 , 124 , 13390-13391. 5. Arisawa, Y. Terada, K. Takahashi, M. Nakagawa, A. Nishida, J. Org. Chem. , 2006 , 26 , 4255-4261. 6. M. Grant, G. C. Lloyd-Jones, unpublished results, 2022.
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