The primary alcohol acceptorless dehydrogenative coupling reaction (ADC) to ester is an environmentally friendly atom-efficient catalytic process as this simultaneously produces hydrogen as the sole by-product. In most cases, efficient catalytic systems rely on the metal-ligand cooperation concept (MLC) where the ligand acts as a proton acceptor and the metal as a hydride acceptor.[ii] Notably, PNP pincer-supported ruthenium complexes have been found to be very active for this reaction, so far in the presence of a base.[iii] (Image to insert) In this contribution, the preparation and catalytic behavior of (new) ruthenium complexes bearing PNP pincer-type aliphatic framework under base-free conditions will be discussed. Additionally, underlying mechanistic aspects will be addressed through a systematic variation of phosphine substituents and additional anionic co-ligands.[iv] Scope and limitations of this highly topical transformation will be commented. Furthermore, we will also demonstrate that process-related limitations have to be taken into account to discuss the true catalytic activity of these hydrogen-releasing systems. References C. Gunanathan, D. Milstein, Chem. Rev. 2014, 114, 12024−12087. [ii] J. R. Khusnutdinova, D. Milstein, Angew. Chem. Int. Ed. 2015, 54, 12236-12273. [iii] M. Nielsen, H. Junge, A. Kammer, M. Beller, Angew. Chem. Int. Ed. 2012, 51, 5711 –5713. M. Bertoli, A. Choualeb, A. J. Lough, B. Moore, D. Spasyuk, D. G. Gusev, Organometallics 2011, 30, 3479–3482. [iv] L. Zhang, G. Raffa, D. H. Nguyen, S. Desset, R. M. Gauvin, S. Paul, F. Dumeignil, X. Trivelli, L. C. Demailly, P. Fongarland, To be submitted.

Base-free and acceptorless ruthenium-catalyzed dehydrogenative coupling of alcohols to esters

251st National Meeting (2016)

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