Transition metals coordinated to the pi system of arenes function as strong electronwithdrawing groups and favor nucleophilic addition to the arene to give cyclohexadienyl-metal complexes. The regioselectivity of addition is influenced in subtle and indirect ways, compared to the powerful effect on both reactivity and regioselectivity of electron-withdrawing groups attached to the sigma bond system of the arene. The intermediate cyclohexadienyl complexes can be processed in several ways, leading to several distinct synthesis methods. Useful reactivity is known for several metal systems and each is discussed for specific reaction types. The presence of a fluoro or chloro substituent on the arene allows an effective analog of classical S N Ar reactivity, with a wide range of nucleophiles including simple amines, alkoxides, and carbon anions. Another general process is the addition/protonation protocol, where a hydrogen substituent on the arene is replaced by a nucleophile. This opens new questions of regioselectivity since the typical arene ligand has several hydrogens which are candidates for substitution. The formation of five-and six-membered rings by both general mechanisms are known. Less general indirect mechanisms (e.g., tele substitution) have also been defined.
Partnerwechsel: Beim Zersetzen des Olefinmetathesekatalysators [(biph)(PCy3)Cl2RuC(H)Ph] (biph=N,N′‐Diphenylbenzimidazol‐2‐yliden, Cy=Cyclohexyl) wird der Benzylidenligand in eine ortho‐C‐H‐Bindung einer N‐Phenylgruppe des biph‐Liganden eingeschoben. Außerdem inseriert das Rutheniumzentrum in eine ortho‐C‐H‐Bindung des anderen N‐Phenylrings, wobei ein fünfgliedriger Metallacyclus mit Ru‐C‐Bindung entsteht (siehe Schema).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.