Olefins catalytic isomerizations

The Homogeneous Catalytic Isomerization of Olefins by Transition Metal Complexes... 

Constrained geometry chromium alkyls catalyzed the polymerization of ethylene however, the reaction was relatively slow, and elevated pressures (PC2H4 = 500 psi) were required to generate significant amounts of polymer. Not surprisingly then, no homopolymoization or copolymerization of a-olefins was observed. Instead, catalytic isomerization and dimerization of the alkyl-substituted olefins was found. 

RCH [Ruhrchemie] A process for increasing the octane rating of gasolines by catalytic isomerization of the olefin fraction, the double bonds migrating from the terminal positions. Developed by Ruhr Chemie in the 1940s. 

S. Otsuka and K. Tani, Asymmetric Catalytic Isomerization of Functionalized Olefins, in J. D. Morrison, ed., Asymmetric Synthesis, Vol. 5, Chap. 6, Academic Press, New York, 1985. 

The catalytic isomerization reation of olefins is caused by either an associative or a dissociative mechanism. The associative mechanism involves either dissociative mechanism involves allylic intermediates, as described in Scheme 2, where M—H and M represent active sites. 

Isomerization of terminal olefins was achieved with the system Ln(C5H5)3/NaH (Ln = Y, Er, Lu). The reactions were carried out at 45 °C in THF and afforded cis- and frans-2-alkenes in very good yields. The catalytic isomerization may occur via organolanthanide hydride intermediates. The proposed mechanism is depicted in Scheme 9 [73]. 

It has been our goal to design a catalytic system theoretically. To the end of this goal, we have so far analyzed the organometallic reactions by using the ab initio MO calculations. Recently, we have completed the theoretical study of the catalytic cycle of hydrogenation by the Wilkinson catalyst (2), of which mechanism has been proposed by Halpern (3). This catalytic cycle shown in Scheme 1 consists of oxidative addition of H, coordination of olefin, olefin insertion, isomerization, and reductive elimina-... 

The oxidative addition of an allylic carbon-hydrogen bond to a transition-metal complex has been frequently invoked in the mechanism of the catalytic isomerization of olefins under hydride-free conditions. 

On the other hand, catalytic isomerization of olefin by pentacarbonyliron can also occur (eq (2)) [18]. 

A solid superbase whose basicity (H ) is higher than 37 has been prepared by the successive treatment of y -alumina with alkali metal hydroxide and alkali metal at 200-600t under nitrogen. The solid base has been found to be highly effective in the catalytic isomerization of olefinic double bonds and in the side-chain alkylation of alkylbenzenes with olefins. 

Photoinduced Catalytic Isomerization of Olefins with Metal Carbonyls 407... 

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