Hetero-ene Metathesis

Metathesis of double bonds has enabled innovation in a broad range of fields: from materials science to medicine. However, this chemistry has largely focused on alkenes rather than hetero-enes, or heteroatom-containing double bonds. Yet, the ability to do hetero-ene metathesis could grant access to valuable heteroatom-rich molecules. Catalysis of double bond metathesis has classically, though not exclusively, relied on the [2+2] cycloaddition/elimination mechanism, which in the case of olefins involves transition metal alkylidenes. However, this mechanism may not be ideal for some hetero-enes, nor is it uniquely suited for the purposes of metathesis: other mechanisms are feasible and, in some cases, precedented. In this Perspective, we present a general framework for mechanistic design that would apply to hetero-ene metathesis, with examples of reported transformations that justify this classification. Advantages, challenges, and opportunities within each class of mechanisms are also outlined. We hope that this Perspective will catalyze further research in this burgeoning field.