An Enyne metathesis is an organic reaction taking place between an alkyne and an alkene with a metal carbene catalyst forming a butadiene. This reaction is a variation of olefin metathesis.
The general scheme is given by scheme 1:
When the reaction is intramolecular (in an enyne) it is called ring-closing enyne metathesis or RCEYM (scheme 2):
with Y representing oxygen or nitrogen and n an integer.
The reaction was first described in 1985 with the conversion of biphenyl 3.1 to a phenanthrene in scheme 3:
The carbene is a tungsten carbonyl when used in stoichoimetric amounts (1 equivalent) yields 41% of the phenanthrene 3.2 and when used in catalytic amounts phenanthrene 3.3. The stereoselectivity of this reaction is large with the metal atom exclusively adding to one of the alkyne carbon atoms in the initial reaction step.
Read more about Enyne Metathesis: Reaction Mechanism, Scope