Cyclooctene, epoxidation selectivity

The MCM samples show about 90-95% cyclooctene epoxidation with TBHP, with nearly 100% selectivity after a reaction time of 24 h (entries 2 and 3, Table 7). Conversion is lower with the SBA-15 catalysts (entry 4, Table 7). The TOPS are about one order of magnitude lower than the respective homo-... 

Materials synthesised by autocatalysis provide high activity (100% conversion in 3 h) and selectivity (100%) for cyclooctene epoxidation with TBHP, as well as excellent recycling ability (the catalytic properties are almost fully recovered after three rims). 

The high epoxidation selectivity of cyclooctene was investigated computationally. Four different chiral conformations and two enantiomeric forms of each conformation were identified. Ring inversion further increased the degeneracy, yielding a total of 16 conformers. An evaluation of microcanonical partition functions quantified the entropy contributions and therefore the equilibrium composition at different temperatures could be calculated. The results suggested that the high epoxidation selectivity for cyclooctene is related to a poor (Tc-ati c-c orbital overlap in the predominant conformation. ... 

Que and coworkers reported on a similar monomeric iron complex, formed with the BPMEN ligand but without acetic acid [128]. This complex was able to epoxidize cyclooctene in reasonably good yield (75%), but at the same time a small amount of the ris-diol (9 %) was formed. This feature observed with this class of complexes has been further studied and more selective catalysts have been prepared. Even though poor levels of conversion are often obtained with the current... 

Srinivasan and Ford [158] reported that epoxidation of cyclooctene using excess H202 was catalyzed by polymolybdate such as [Mo7024]6 tethered on the colloidal polymer with alkylammo-nium cations. Cyclooctene was oxidized to give 1,2-epoxy cyclooctane with >99% selectivity at 90% conversion for 24 h at 313 k ... 

Alternatively, in 2000 researchers from Peroxid Chemie reported that with the catalytic system [Oct3NMe]3[PWi204o] (0.06 mol%) using 70% H2O2, olefins could be converted to the corresponding epoxides in high yields and selectivities (e.g. cyclooctene ... 

Mimoun and coworkersdescribed the first well-defined example of a d° metal aUtylperoxidic species 49 which epoxidized simple olefins with high selectivity. Several features of the epoxidation performed by 49 resemble those of the Halcon catalytic epoxidation process " . Novel tungsten complexes containing 2 -pyridyl alcoholate ligands like 50 have been synthesized and tested as catalysts in the epoxidation of cw-cyclooctene with TBHP in the absence of solvent . The system displayed modest catalytic activity (100% conversion in 60 h) but excellent product selectivity. 

Recycling experiments with MnClj2TMPS immobilized on methylated PVP, Recycling experiments were performed by re-using four times the same MnQi2TMPS catalyst supported on methylated PVP in the PhIO epoxidation of cyclooctene. For [MnCli2TMPS-PVPMe ][TsO"], it should be noted that the first two cycles are exactly the same, only a small activity decrease is observed for the third run. With 1 jimol of MnCli2TMPS immobilized on [PVPMe "][TsO ] the total epoxide production after 4 runs is 1970 jimol. The overall selectivity based on PhIO is 65%. ... 

Dramatic shape selectivities in competitive olefin epoxidation was observed with picnic basket metalloporphyrins312 313 designed to exclude bulky axial ligands on one sterically protected porphyrin face. When oxidized with PhIO in acetonitrile in the presence of the rigid p-xylyl-strapped porphyrin, cis-2-octene reacted selectively versus ds-cyclooctene or 2-methyl-2-pentene, giving >1000 reactivity ratios.313,314 Some immobilized manganese(III) porphyrins proved to be as efficient as their homogeneous equivalents in epoxidation with PhIO.151,315... 

Gold-catalyzed oxidation of styrene was firstly reported by Choudhary and coworkers for Au NPs supported on metal oxides in the presence of an excess amount of radical initiator, t-butyl hydroperoxide (TBHP), to afford styrene oxide, while benzaldehyde and benzoic acid were formed in the presence of supports without Au NPs [199]. Subsequently, Hutchings and coworkers demonstrated the selective oxidation of cyclohexene over Au/C with a catalytic amount of TBHP to yield cyclohexene oxide with a selectivity of 50% and cyclohexenone (26%) as a by-product [2]. Product selectivity was significantly changed by solvents. Cyclohexene oxide was obtained as a major product with a selectivity of 50% in 1,2,3,5-tetramethylbenzene while cyclohexenone and cyclohexenol were formed with selectivities of 35 and 25%, respectively, in toluene. A promoting effect of Bi addition to Au was also reported for the epoxidation of cyclooctene under solvent-free conditions. 

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