Insertion of (E)-(1,2-dihalovinyl)lithium and (2-haloethynyl)lithium into zirconacycles

Abstract

Insertion of (E)-(1,2-dihalovinyl)lithium into zirconacyclopentenes was followed by elimination of halide to afford an alkyne which inserts intramolecularly into the resulting carbon–zirconocenium bond to give a methylenecyclopentene, whereas insertion of (2-haloethynyl)lithium gives the same product via a zirconocene alkenylidene.