Selective Cross-Metathesis of Highly Chelating Substrates in Aqueous Media

The role of non-productive chelation in olefin metathesis has been investigated for a variety of highly functionalized substrates in aqueous environment. Using a morpholine-substituted catalyst, the reactivity of oligoethylene glycols and oligopeptides was evaluated, either in self-metathesis protocols, or in cross-metathesis processes with allyl alcohol. The limited reactivity of the substrates in self-metathesis reactions could be utilized to achieve selectivity in cross-metathesis with more reactive alkenes. With 2.5 mol % catalyst loading, up to 62% conversion to cross-metathesis products could be observed for the model systems within 5 h. Overall, this study opens up new potential avenues for olefin metathesis in the field of chemical biology where chelating substrates are omnipresent.