Pushing the limits of Ru-Based Assisted Tandem metathesis-hydrogenation

“Assisted tandem catalysis” is a term proposed by Fogg et al.[1] for processes where a catalyst used to perform a first reaction is converted into a new species able to catalyze a second reaction upon the addition of a reagent or a change in the experimental conditions (Scheme 1). Scheme 1. Assisted Tandem Catalysis The tandem “metathesis-hydrogenation” is an example of assisted tandem catalysis.[2] Once the metathesis reaction is complete, the addition of H2 converts the Ru species into a hydrogenation catalyst. Up until now, most of the studies have focused on the hydrogenation of the olefin formed during the metathesis steps. However, Ru is capable of much more challenging hydrogenations such as asymmetric hydrogenation [3] or ester hydrogenation.[4] In this oral communication, we will present our successful high-throughput screening for triggers to turn Grubbs metathesis catalysts into catalysts for asymmetric hydrogenation and ester hydrogenation. Several examples of the corresponding tandem catalysis will be disclosed as well as our initial efforts to identify the active species via kinetic measurements, NMR and high resolution mass spectrometry (Scheme 2).