Cross metathesis and ring-closing metathesis are driven by the entropically favored evolution of ethylene or propylene, which can be removed from the system because they are gases because of this cm and rcm reactions often use alpha-olefins. Olefin metathesis is an organic reaction that entails the redistribution of fragments of alkenes (olefins) by the scission and regeneration of carbon-carbon double bonds   because of the relative simplicity of olefin metathesis, it often creates fewer undesired by-products and hazardous wastes than alternative organic reactions. Ring-closing metathesis is a variant of the olefin metathesis reaction in which alkylidene moieties are exchanged to form a ring the most common catalysts for this reaction are complexes of molybdenum or ruthenium. Ring opening metathesis can employ an excess of a second alkene (for example ethene), but can also be conducted as a homo- or co-polymerization reaction the driving force in this case is the loss of ring strain.
Ring-closing metathesis, or rcm, is a widely used variation of olefin metathesis in organic chemistry for the synthesis of various unsaturated rings via the intramolecular metathesis of two terminal alkenes, which forms the cycloalkene as the e-or z-isomers and volatile ethylene.
Ring closing metathesis (rcm) the ring-closing metathesis (rcm) allows synthesis of 5- up to 30-membered cyclic alkenes the e/z -selectivity depends on the ring strain. Olefin metathesis in organic synthesis wendy jen macmillan group meeting january 17, 2001 i well-defined alkene metathesis catalysts ii applications of olefin metathesis a ring closing metathesis b cross metathesis c ring opening metathesis recent reviews: furstner, a angew chem int ed 2000, 39, 3013. Wood and coworkers devised an ingenious approach involving a ring-opening/cross metathesis and a ring-closing metathesis step (scheme 2) with only 2 mol % of the grubbs catalyst (1st generation), the norbornene derivative afforded the desired dienes in nearly quantitative yield.
A simple ring closing metathesis problem (including mechanism.