Fast-Initiating, Ruthenium-based Catalysts for Improved Activity in Highly E-Selective Cross Metathesis
Ruthenium-based olefin metathesis catalysts bearing dithiolate ligands have been recently employed to generate olefins with high E-selectivity (>99% E) but have been limited by low to moderate yields. In this report, ^1H NMR studies reveal that a major contributing factor to this low activity is the extremely low initiation rates of these catalysts with trans olefins. Introducing a 2-isopropoxy-3-phenylbenzylidene ligand in place of the conventional 2-isopropoxybenzylidene ligand resulted in catalysts that initiate rapidly under reaction conditions. As a result, reactions were completed in significantly less time and delivered higher yields than those in previous reports while maintaining high stereoselectivity (>99% E).
© 2017 American Chemical Society. Received: October 31, 2016; Publication Date (Web): January 20, 2017. We acknowledge funding from the Office of Naval Research (N00014-14-1-0650) and the NSF (CHE-1502616). T.S.A. is grateful for support from the National Science Foundation through a Graduate Research Fellowship. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. Materia, Inc. is thanked for generous donations of catalysts 2a and 3a. M. A. Pribisko, B. L. Quigley, and R. M. B. Silva are thanked for their input on this manuscript. J. R. Sampson, W. J. Wolf, N. F. Nathel, and T. P. Montgomery are thanked for helpful discussions. The authors declare no competing financial interest.
Supplemental Material - ja6b11330_si_001.pdf