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In organic chemistry, 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. [ 1 ] [ 2 ] Because of the relative simplicity of olefin metathesis, it often creates fewer undesired by-products and hazardous wastes than alternative ...
Ring-closing metathesis (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.
The mechanism of homogeneous ring-opening metathesis polymerization is well-studied. It is similar to any olefin metathesis reaction. Initiation occurs by forming an open coordination site on the catalyst. Propagation happens via a metallacycle intermediate formed after a 2+2 cycloaddition. When using a G3 catalyst, 2+2 cycloaddition is the ...
Besides olefin metathesis (described above), many pericyclic reactions can be used such as the ene reaction and the Cope rearrangement. Cope rearrangement of divinylcyclobutane to cyclooctadiene. In the Diels–Alder reaction, a cyclohexene derivative is prepared from a diene and a reactive or electron-deficient alkene.
Carbonyl olefin metathesis is a type of metathesis reaction that entails, formally, the redistribution of fragments of an alkene and a carbonyl by the scission and regeneration of carbon-carbon and carbon-oxygen double bonds respectively.
Olefin metathesis is a formal exchange of the alkylidene fragments in two alkenes. It is a catalytic reaction with carbene, or more accurately, transition metal carbene complex intermediates. In this example (ethenolysis, a pair of vinyl compounds form a new symmetrical alkene with expulsion of ethylene.
The mechanism for ROMP follows similar pathways as olefin metathesis. The initiation process involves the coordination of the cycloalkene monomer to the metal alkylidene complex , followed by a [2+2] type cycloaddition to form the metallacyclobutane intermediate that cycloreverts to form a new alkylidene species.
Catalytic cycle of olefin metathesis. The metal complex alternated between a metallocyclobutane ring and carbene complex, catalyzing the formation of new carbon-carbon double bonds. The dominant application of metal carbenes involves none of the above classes of compounds, but rather heterogeneous catalysts used for alkene metathesis for the ...