Metal carbenes in enyne metathesis: Synthetic and mechanistic studies

Intermolecular (cross) enyne metathesis between dienes and alkynes is an effective method for ring synthesis giving cyclodienes. The enyne metathesis is initiated by the Grubbs carbene complex (H₂IMes)(Cy₃P)Cl₂Ru{double bond, long}CHPh (Ru gen-2), which produces vinyl carbene intermediates. Our desire to develop the cross enyne metathesis into an efficient and useful organic reaction has improved our understanding of both the scope and mechanism of enyne metathesis. This mini-review is based on my lecture given at the ISOM16 meeting in Poznan in August of 2005, and is not meant as a comprehensive review of the subject. The mini-review focuses on the problems we encountered, provides background and context found in the relevant literature and details the three approaches we pursued in solving the ring synthesis research problem. These studies led to kinetic investigation of enyne metathesis reaction mechanism, which is also summarized.