Metal ion catalysis of oxygen transfer reactions. I. Vanadium catalysis of the epoxidation of cyclohexene

Gould, Edwin S.; Hiatt, R.; Irwin, Katherine C.

doi:10.1021/ja01019a011

Cited by 103 publications

(30 citation statements)

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“…This mechanism was already proposed in the early seventies [4,[39][40][41][42][43]. In mechanism Ia the electron-deficient oxygen of the hydroperoxide ROOH is placed in the vicinity of the double bond in the transition state.…”

Section: Epoxidation Mechanismmentioning

confidence: 99%

“…Many catalytic systems based on transitionmetal complexes of Mo, Ti, W and V have been reported and found to be very effective and selective for the epoxidation of a wide range of (cyclo)alkenes using hydroperoxides as oxidant [1][2][3]. The reaction chemistry of vanadyl acetylacetonate (VO(acac) 2 ) as catalyst for the oxidation of cyclohexene with hydrogen peroxide or tert-butyl hydroperoxide (TBHP) as oxidant has been the subject of several experimental studies [4][5][6][7][8]. Recently, the homogeneous VO(acac) 2 /TBHP system and the porous metal organic framework type catalyst MIL-47 [9] have been compared for their cyclohexene epoxidation activity and they showed similar conversion patterns [10,11].…”

Section: Introductionmentioning

confidence: 99%

“…VO(acac) 2 is readily oxidized to V +V complexes upon treatment with a peroxide and vanadium(V) complexes have been found to act as catalyst precursors in various oxidation reactions such as bromination reactions, epoxidations of alkenes and allylic alcohols, oxidations of sulfides to sulfoxides and sulfones, hydroxylations of alkanes and arenes, and oxidations of primary and secondary alcohols to the corresponding aldehydes and ketones [13,15]. The VO(acac) 2 -catalyzed epoxidation of allylic alcohols with alkyl hydroperoxides provides a useful route to epoxidize alcohols [4,[15][16][17]. By using proline-derived hydroxamic acids as chiral ligands, even higher enantioselectivities (up to 80% enantiomeric excess) could be achieved [12,17].…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, certain studies have tried to unravel the initial steps in the reaction of VO(acac) 2 with TBHP [7,8]. The active intermediates were widely accepted to be vanadium(+V) alkylperoxo complexes in the VO(acac) 2 /TBHP [4,16,17,22] and VO(acac) 2 /TBHP/ligand [24][25][26][27][28] catalytic systems. More specifically, Talsi et al [8] investigated the role of alkylperoxo complexes for the cyclohexene epoxidation with organic hydroperoxides in presence of VO(acac) 2 in detail by NMR and EPR.…”

Section: Introductionmentioning

confidence: 99%

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Mechanistic insight into the cyclohexene epoxidation with VO(acac)2 and tert-butyl hydroperoxide

Vandichel

Leus

Voort

et al. 2012

Journal of Catalysis

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The epoxidation reaction of cyclohexene is investigated for the system vanadyl acetylacetonate (VO(acac) 2 ) as catalyst with tert-butyl hydroperoxide (TBHP) as oxidant with the aim to identify the most active species for epoxidation and to retrieve insight into the most plausible epoxidation mechanism. The reaction mixture is composed of various inactive and active complexes in which vanadium may either have oxidation state +IV or +V. Inactive species are activated with TBHP to form active complexes. After reaction with cyclohexene each active species transforms back into an inactive complex which may be reactivated again. The reaction mixture is quite complex containing hydroxyl, acetyl acetonate, acetate or a tert-butoxide anion as ligands and thus various ligand exchange reactions may occur among active and inactive complexes. Also radical decomposition reaction allow transforming V +IV to V +V species. To obtain insight into the most abundant active complexes, each of previous transformation steps has been modeled through thermodynamic equilibrium steps. To unravel the nature of the most plausible epoxidation mechanism, first principle chemical kinetics calculations have been performed on all proposed epoxidation pathways. Our results allow to conclude that the concerted Sharpless mechanism is the preferred reaction mechanism and that alkylperoxo species V +IV O(L)(OOtBu) and V +V O(L 1 )(L 2 )(OOtBu) species are most abundant. At the onset of the catalytic cycle vanadium +IV species may play an active role but as the reaction proceeds, reaction mechanisms that involve vanadium +V species are preferred as the acetyl acetonate is readily oxidized. Additionally an experimental IR and kinetic study has been performed to give a qualitative composition of the reaction mixture and to obtain experimental kinetic data for comparison with our theoretical values. The agreement between theory and experiment is satisfactory.

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Section: Epoxidation Mechanismmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Mechanistic insight into the cyclohexene epoxidation with VO(acac)2 and tert-butyl hydroperoxide

Vandichel

Leus

Voort

et al. 2012

Journal of Catalysis

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“…The quantitative values of our calculations can indirectly be validated with the results of a kinetic study on the epoxidation of cyclohexene with VO(acac) 2 . Gould et al suggested that vanadium is probably converted to the +V oxidation state and remains in that state throughout 45 . This is in full agreement with the situation encountered in the epoxidation reactions 10  11 and 12  11.…”

Section: Reaction Kinetics: Direct Versus Radical Pathwaymentioning

confidence: 99%

The coordinatively saturated vanadium MIL-47 as a low leaching heterogeneous catalyst in the oxidation of cyclohexene

Leus

Vandichel

Liu

et al. 2012

Journal of Catalysis

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A Metal Organic Framework, containing coordinatively saturated V +IV sites linked together by terephthalic linkers (V-MIL-47) is evaluated as a catalyst in the epoxidation of cyclohexene. Different solvents and conditions are tested and compared. If the oxidant TBHP is dissolved in water, a significant leaching of V-species into the solution is observed and also radical pathways are 2 prominently operative leading to the formation of an adduct between the peroxide and cyclohexene. If however the oxidant is dissolved in decane, leaching is negligible and the structural integrity of the V-MIL-47 is maintained during successive runs. The selectivity towards the epoxide is very high in these circumstances. Extensive computational modelling is performed to show that several reaction cycles are possible. EPR and NMR measurements confirm that at least two parallel catalytic cycles are co-existing: one with V +IV sites and one with pre-oxidized V +V sites, and this in complete agreement with the theoretical predictions.

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2,4-Pentanedione

Harris

2001

Encyclopedia of Reagents for Organic Synthesis

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Metal ion catalysis of oxygen transfer reactions. I. Vanadium catalysis of the epoxidation of cyclohexene

Cited by 103 publications

References 0 publications

Mechanistic insight into the cyclohexene epoxidation with VO(acac)2 and tert-butyl hydroperoxide

Mechanistic insight into the cyclohexene epoxidation with VO(acac)2 and tert-butyl hydroperoxide

The coordinatively saturated vanadium MIL-47 as a low leaching heterogeneous catalyst in the oxidation of cyclohexene

2,4-Pentanedione

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