This account describes recent development in carbon-carbon bond cleavage re
actions and selective transformation of 5-membered zirconacycles, including
zirconacyclopentanes, zironacyclopentenes, and zirconacyclopentadienes. Th
ese zirconacycles can be prepared by coupling of unsaturated compounds such
as alkenes and/or alkynes, but the zirconacycles also undergo beta,beta'-C
-C bond cleavage, which has been further applied to organic transformation
reactions. Combination of the beta,beta'-C-C bond cleavage and the C-C bond
formation on zirconocene provided a highly selective and novel transformat
ion. Vinylzirconation of alkynes, regioselective allylzirconation of alkyne
s, and coupling of alkynes with nitriles or ketones were achieved by this m
ethod. Zirconacyclopentadienes prepared symmetrically or unsymmetrically we
re converted into naphthalene, diene, and benzene derivatives. Preparation
of benzene derivatives from three different alkynes was performed by combin
ation of C-C bond cleavage and C-C bond formation on zirconocene in one-pot
in high yield with excellent selectivity.