Zirconacyclopentenes Zirconacyclopropanes

Alternatively, functionalized zirconacyclopropene and zirconacyclopropane can be easily prepared by using the Negishi reagent (Cp2ZrCl2 + 2 -BuLi) [47]. In the presence of an additional unsaturated system, a carbocyclization reaction occurs to lead to the corresponding zirconacyclopentene or zirconacyclopentane derivatives [47]. When the substrate possesses a stereocontrol unit such as an amide moiety, a diastereoselective carbocyclization occurs [48] (Scheme 12.35). 

---