Cyclohexyne
Cyclohexyne is a highly reactive, strained cyclic alkyne with the molecular formula and the structure of a six-membered carbon ring containing a triple bond. It is a member of the class of compounds known as arynes and is best classified as a six-membered cyclic alkyne. Due to its high ring strain and instability, cyclohexyne cannot be isolated under normal conditions and exists only as a short-lived reactive intermediate in certain organic reactions.
Synthesis
Cyclohexyne cannot be stored or isolated due to its extreme instability. It is generated in situ through the elimination of hydrogen halides from suitable precursors. Other methods include the use of organolithium reagents or photolytic or thermal activation of precursor molecules.Cyclohexyne as a complex ligand
The formation of metal complexes stabilizes cyclohexyne. A platinum complex of cyclohexyne can be prepared by elimination from 1-bromocyclohexene with lithium diisopropylamide in the presence of trisplatinum. An alternative synthetic method is the reduction of 1,2-dibromocyclohexene with sodium amalgam in the presence of trisplatinum. Such a complex can also be prepared by trapping with trisplatinum when cyclohexenylphenyliodonium tetrafluoroborate is used as the starting material for cyclohexyne.Another complex, in this case with zirconium, can be prepared starting from methylzirconocene chloride by reacting it first with cyclohexenyllithium and then with trimethylphosphine.