Olefin metathesis

Olefin metathesis exchanges carbon–carbon double-bond partners between alkenes through metal-carbene intermediates, producing new alkenes.

Metal carbene: A metal complex containing a carbon atom bonded to the metal by a multiple-bond character. The metal-bound carbon exchanges alkene partners during the metathesis cycle.
Ring-closing metathesis: An intramolecular alkene metathesis that closes a ring while releasing a small alkene. It uses the exchange reaction to construct cyclic molecules from dienes.
Yves Chauvin: A French chemist who proposed the metal-carbene mechanism for olefin metathesis. His mechanistic proposal unified previously disconnected metathesis observations.
Wittig reaction: A carbonyl olefination that uses a phosphorus ylide to form an alkene and a phosphorus–oxygen product. Unlike metathesis, it forms a double bond by replacing a carbonyl oxygen with a carbon substituent.
Chauvin mechanism: A catalytic cycle in which metal carbenes and alkenes form metallacyclobutanes that fragment into new alkene pairs. It explains how metathesis exchanges alkene fragments without breaking the carbon skeleton arbitrarily.
Ring-opening metathesis polymerization: A chain-growth polymerization that opens strained cyclic alkenes through metathesis. Metathesis converts cyclic monomers into polymers while retaining their unsaturation.
Robert H. Grubbs: An American chemist who developed practical ruthenium catalysts for olefin metathesis. His catalysts made the reaction more tolerant of functional groups and easier to use.
Heck reaction: A palladium-catalyzed coupling of an aryl or vinyl halide with an alkene to form a substituted alkene. It makes carbon–carbon bonds by coupling fragments, rather than exchanging alkene partners.
Metallacyclobutane: A four-membered ring containing a metal atom and three carbon atoms. Its formation and cycloreversion connect the starting alkene to the exchanged product.
Cross metathesis: An alkene-exchange reaction between two different alkenes that forms crossed products. It directs the reaction toward intermolecular exchange between distinct alkene partners.

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