Titanium complexes, isomerization

Similar to IFP s Dimersol process, the Alphabutol process uses a Ziegler-Natta type soluble catalyst based on a titanium complex, with triethyl aluminum as a co-catalyst. This soluble catalyst system avoids the isomerization of 1-butene to 2-butene and thus eliminates the need for removing the isomers from the 1-butene. The process is composed of four sections reaction, co-catalyst injection, catalyst removal, and distillation. Reaction takes place at 50—55°C and 2.4—2.8 MPa (350—400 psig) for 5—6 h. The catalyst is continuously fed to the reactor ethylene conversion is about 80—85% per pass with a selectivity to 1-butene of 93%. The catalyst is removed by vaporizing Hquid withdrawn from the reactor in two steps classical exchanger and thin-film evaporator. The purity of the butene produced with this technology is 99.90%. IFP has Hcensed this technology in areas where there is no local supply of 1-butene from other sources, such as Saudi Arabia and the Far East. 

The enantiopure acyclic and cyclic allyl sulfoximines 13 and 14, respectively, required for the synthesis of the corresponding titanium complexes 1 and 2, are available from sulfoximine 12 [13] and the corresponding aldehydes and cycloal-kanones by the addition-elimination-isomerization route, which can be carried... 

However, a more detailed study of the reaction of the mono(allyl)titanium complexes -19 carrying different alkyl groups at the double bond with different aldehydes revealed in some cases the highly diastereoselective (>98%) formation of significant amounts of the isomeric homoallyl alcohols 4 besides 6 (Table 1.3.1). 

Because of the observation of a fast equilibrium between the C-titanium complexes 19A and 19C and the N-titanium ylides 19B, the reactivity model depicted in Scheme 1.3.16 was proposed in order to account for the regio- and diastereose-lectivity observed in the reaction of 19 with aldehydes. This model, which is based on the assumption of the operation of the Curtin-Hammett principle (that is, the reactions of 19A, 19B, and 19C with aldehydes are significantly slower than their isomerization), features the six-membered cyclic chair-like transition states... 

Asymmetric isomerization of 4-terr-butyl-l -vinylcyclohexane (6) catalyzed by bis(indenyl)-titanium complex (8) bearing a chiral bridging moiety afforded (S)-4-fcrr-buty 1-1 -ethy lidenecy-clohexane (7) with up to 80% ee (Scheme 3A.3).3,4... 

An asymmetric variant of double-bond isomerization could be achieved with the chiral a ra-bis(indenyl)titanium complex [43]. After activation with LiAlH4 it isomerizes m 50,traw5-4-tert-butyl-l-vinyl-cyclohexane to the 5-alkene with remarkable enantioselectivity (80 % ee). 

An efficient isomerization of aliphatic and cyclic olefins is achieved using well-defined bis-Cp alkyne titanium complexes as catalysts. These complexes isomerize 1-alkenes to internal alkenes under mild conditions. The titanium complex can be recovered quantitatively. Cyclic olefins, for example, cyclohexadienes, also undergo... 

Titanium complexes of oxacalix[3]arenes - synthesis and mechanistic studies of their dynamic isomerization, P. D. Hampton, C. E. Daitch, T. M. Alam, Z. Bencze and M. Rosay, Inorg. Chem., 1994, 33, 4750. 

The reactions of titanium-alkylidenes prepared from thioacetals with unsymmetrical olefins generally produce complex mixtures of olefins. This complexity arises, at least in part, from the concomitant formation of the two isomeric titanacyclobutane intermediates. However, the regiochemistry of the titanacyclobutane formation is controlled when an olefin bearing a specific substituent is employed. Reactions of titanocene-alkylidenes generated from thioacetals with trialkylallylsilanes 30 afford y-substituted allylsilanes 31, along with small amounts of homoallylsilanes 32 (Scheme 14.16) [28]. 

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