Ring-closing metathesis reaction metal catalysts

Conformationally constrained a-Boc-aminophosphonates (387), (388) (389), (390) and (391) were made via a transition metal catalysed Curtins rearrangement. The conformational constraint involved either a ring-closing metathesis reaction catalysed by the first generation Grubbs catalyst or intramolecular cyclopropanation mediated by Rh2(OAc)4 (Figure 66). ... 

Olefin metathesis is a unique carbon skeleton redistribution in which unsaturated carbon-carbon bonds are rearranged in the presence of metal carbene complexes. With the advent of efficient catalysts, this reaction has emerged as a powerful tool for the formation of C-C bonds in chemistry [1]. Olefin metathesis can be utilized in five types of reactions ring-closing metathesis (RCM), ring-opening metathesis (ROM), respective ringopening metathesis polymerization (ROMP), cross-metathesis (CM), and acyclic diene metathesis polymerization (ADMET). 

Structures 25.55 (Grubbs catalyst) and 25.56 (a complex developed by Schrock) show two important carbene compounds that are used as catalysts in alkene olefin) metathesis, i.e. metal-catalysed reactions in which C=C bonds are redistributed. Examples include ring-opening metathesis polymerization (ROMP) and ring-closing metathesis (RCM). We look at these reactions in detail in Section 26.3. 

---