From Enyne Metathesis To Aryne Chemistry

Enyne metathesis is a process by which alkenes and alkynes are merged together with the catalytic action of metal alkylidene complexes to form 1,3-dienes. In light of developing new eneyne metathesis, more extended unsaturation was incorporated into the yne-component such that the enyne metathesis can be coupled with [1,3]-metallotropic shift process. Due to their effectiveness in forming conjugated 1,3-dienes and 1,3-enynes, enyne metathesis and metallotropic shift have been widely exploited in our research including the total synthesis of amphidinolide V.

While exploring the reactivity of various ene-components with the yne component of extended conjugation in enyne metathesis, several unusual reactions were discovered. With ethylene as the ene-component, metathesis of the conjugated alkyne containing 1,3-diynes was completely shunted and hydrovinylation occurred exclusively. On the other hand, without the alkene component, the Grubbs ruthenium alkylidene complexes promote the dehydro Diels-Alder reaction to generate putative aryne intermediates, which are then hydrohalogenated by halohydrocarbons to form a variety of hydrohalogenated aromatic products.

In this talk, I will present a recent application of ruthenium alkylidene-based enyne metathesis for the synthesis of amphidinolide V, which will then be followed by several discoveries of unprecedented reactions that are efficiently catalyzed by Grubbs-type alkylidenes.