1-hexene epoxidation

When epoxides such as tra s-3-hexene-epoxide 1885 are heated to 65 °C with hexamethyidisiiane 857 and potassium methoxide in anhydrous HMPA, trimethylsilyl potassium 1882 is generated in situ to open the epoxide rings and give 1886, which subsequently looses potassium trimethylsilanolate 97 to afford olefins with inverted stereochemistry, for example as cis-3-hexene 1887, in high yield [103]. The reaction also proceeds at 65 °C in THF, rather than HMPA, if 18-crown-6 is added [103a] (Scheme 12.29). 

Chlorocyclohexane Chlorocyclohexane Bromocyclohexane E-3-hexene epoxide Z-3-hexene epoxide E-3-methyl-2-pentene epoxide Z-3-methyl-3-pentene epoxide O... 

The activity data confirm that an IR absorption band at 960 cm" is a necessary condition for titanium silicates to be active for the selective oxidation of hydrocarbons with aqueous H2O2 as suggested by Huybrechts et al. (9). However, this band is not a sufficient condition for predicting the activity of the TS-1 catalyst. Although TS-l(B) and TS-l(C) show intensities for the 960 cm- band similar to TS-1 (A), their activities are different First of all, the reaction data reveal that TS-1 (A) is much more active than TS-l(B) for phenol hydroxylation, while both samples show similar activity for n-octane oxidation and 1-hexene epoxidation. Therefore, the presence of the IR band at 960 cm-i in TS-1 catalysts may correlate with the activities for the oxidation of n-octane and the epoxidation of 1-hexene but not for phenol hydroxylation. However, note that the amorphous Ti02-Si02 also has an IR absorption band at 960 cm- and it does not activate either substrate. 

Five generations of mutagenesis ra-Octane, ra-hexane, cydohexane, n-pentane (hydroxylation) [133], benzene, styrene, cydohexene, 1-hexene (epoxidation) [134]... 

A recent elegant example of the tailoring the chemical properties of encapsulated metal complexes is the work of Balkus etal. who prepared and studied perfluorinated phthalocyanine complexes of Fe, Co, Cu and Ru (Scheme 25)[230] in NaX. Perfluorinating the complexes enhances the stability and catalytic activity of the catalysts in the oxyfiinctionalisation of light alkanes. The rapid deactivation of the catalysts based on Fe, Co and Cu Fj Pc complexes was overcome by using Ru as the metal center. Similar catalysts, i.e.,Co-phthalocyanine (Co-Pc) encapsulated in zeolite Y, are active catalysts for cyclohexene and 1-hexene epoxidation (Scheme 27)[231]. Comparison of the activity of free and encapsulated Co-Pc has shown that the interaction with the zeolite stabilizes the complex. Co-Pc is still active after 24 hrs reaction whereas the free complex in solution is virtually inactive after 15 minutes. 

The reactor for HjO-electrolysis used in the epoxidation of alkenes is shown schematically in Figure 2. The anode was prepared from metal blacks (70 mg) mixed with Teflon powder by the hot-press method. The cathode was prepared from a mixture of Pt black, graphite and Teflon powder. Propylene was bubbled into CH Clj (40 ml used as a solvent) in the anode compartment. In the case of 1-hexene epoxidation, 10 ml of the alkene was dissolved in 30 ml of CH2CI2. Argon (98 kPa) and water vapor (4 kPa) were... 

Table 4. Comparison of TS-1 with state-of-the-art homogeneous catalysts for 1-hexene epoxidation with aqueous hydrogen peroxide. 

Mn(TPP)Cl Ascorbate Cyclohexenol Styrene Styrene oxide Cyclohexene, Epoxide CIS and trans stilbenes, Epoxides CIS- and trans-2-hexenes, Epoxides 2,3-Dimethyl-2-butene, Epoxides [83]... 

The ease with which thiophenes are formed in the reaction of acetylenic epoxides " and of polyacetylenes with hydrogen sulfide is of great interest in connection with the biosynthesis of the naturally occurring thiophenes (cf. Section VIH,A) and also of preparative importance. 2-Methyl-l,2-oxido-5-hexene-3-yne (56) in water containing barium hydroxide reacts with HzS at 50°C to give 4-... 

The reactivity of T8[OSiMe2H]g is dominated by its capacity to undergo hydrosilylation reactions with a wide variety of vinyl and allyl derivatives (Figure 30) that have subsequently mainly been used as precursors to polymers and nanocomposites by the introduction of reactive terminating functions as shown in Table 19. For example, T8[OSiMe2H]g has been modified with allyglycidyl ether, epoxy-5-hexene, and 1,2-cyclohexene-epoxide to give epoxy-terminated FOSS. These have then been treated with m-phenylenediamine, with polyamic acids or... 

In this work, highly active epoxidation catalysts, which have hydrophobic surface of TS-1, were synthesized by the dry gel conversion (DGC) method. Ti-MCM-41 was synthesized first by a modifed method and the TS-l/MCM-41 catalysts were subsequently synthesized by the DGC method. The catalysts were characterized by the XRD, BET, FT-IR, and UV-VIS spectroscopy. TS-l/MCM-41 catalysts were applied to the epoxidation of 1-hexene and cyclohexene with aqueous H202to evaluate their activities for the epoxidation reaction. ... 

The catalytic activitira of synfliesized catalysts are given in Table 1. The TS-1 catalyst exhibited the highest epoxide yield and the best catalytic performance for the epoxidation of 1-hexene. The convasion of cyclohexene, however, is the lowest over TS-1. In case of TS-1/MCM-41-A and TS-1/MCM-41-B, the selectivity to epoxide is much hi er than that of Ti-MCM-41. Moreover, the conversion of 1-hexene as well as cyclohexene is found larger on the TS-l/MCM-41-Aand TS-1/MCM-41-B than on other catalysts. While the epoxide yield from 1-hexene is nearly equivalent to that of TS-1, the yield from cyclohexene is much larger than those of the otiier two catalysts. Th e results of olefins epoxidation demonstrate that the TS-l/MCM-41-Aand TS-1/MCM-41-B possess the surface properties of TS-1 and mesoporosity of a typical mesoporous material, which were evidently brou in by the DGC process. 

Titanium containing hexagonal mesoporous materials were synthesized by the modified hydrothermal synthesis method. The synthesized Ti-MCM-41 has hi y ordered hexa rud structure. Ti-MCM-41 was transformed into TS-l/MCM-41 by using the dry gel conversion process. For the synthesis of Ti-MCM-41 with TS-1(TS-1/MCM-41) structure TPAOH was used as the template. The synthesized TS-l/MCM-41 has hexagonal mesopores when the DGC process was carried out for less than 3 6 h. The catalytic activity of synthesized TS-l/MCM-41 catalysts was measured by the epoxidation of 1-hexene and cyclohexene. For the comparison of the catalytic activity, TS-1 and Ti-MCM-41 samples were also applied to the epoxidation reaction under the same reaction conditions. Both the conversion of olefins and selectivity to epoxide over TS-l/MCM-41 are found hi er flian those of other catalysts. 

Hexene, 17 722 20 414 Alfrey-Price parameters, 7 617t catalytic aerogels for epoxidation, l 763t... 

The epoxidation of alkenes using iodosylbenzene, with tetra-n-butylammonium bromide and a manganese or cobalt polytungstate as co-catalysts [24], appears to have little advantage as a synthetic procedure over other methods. n-Hexene produces the oxirane (58%), when catalysed by the manganese salt, whereas norbornene is more readily converted (96%) into the oxirane with the cobalt salt. 

In order to assess whether intramolecular cooperativity could occur within the dendrimeric [Co(salen)]catalyst the HKR of racemic l-cyclohexyl-l,2-ethenoxide was studied at low catalyst concentrations (2xl0 " M). Under these conditions the monomeric [Co(salen)] complex showed no conversion at all, while the dendritic [G2]-[Co(salen)]catalyst gave an impressive enantiomeric excess of 98% ee of the epoxide at 50% conversion. Further catalytic studies for the HKR with 1,2-hexen-oxide revealed that the dendritic catalysts are significantly more active than a dimeric model compound. However, the [Gl]-complex represents already the maximum (100%) in relative rate per Go-salen unit, which was lower for higher generations [G2] (66%) and [G3] (45%). 

Two extreme epoxidation modes, spiro and planar, are shown in Fig. 9 [33, 34, 53, 54, 76-85]. Baumstark and coworkers had observed that the epoxidation of cis-hexene of dimethyldioxirane was seven to nine times faster than the corresponding epoxidation of tran.y-hexene [79, 80]. The relative rates of the epoxidation of cisitrans olefins suggest that spiro transition state is favored over planar. In spiro transition states, the steric interaction for cw-olefm is smaller than the steric interaction for fran -olefm. In planar transition states, similar steric interactions would be expected for both cis- and trans-olefms. Computational studies also showed that the spiro transition state is the optimal transition state for oxygen atom transfer from dimethyldioxirane to ethylene, presumably due to the stabilizing interactions... 

Lee and coworkers have reported on the use of the highly active and selective cobalt(III) catalyst depicted in Fig. 12 for the terpolymerization of propylene oxide and various epoxides with CO2, including cyclohexene oxide, 1-hexene oxide, and 1-butene oxide [61]. Catalytic activities ranged from 4,400-14,000 h at a CO2... 

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