Olefin epoxidation with hydrogen peroxide using octamolybdate-based self-separating catalysts

Abstract

Alkylimidazolium/alkylpyridinium octamolybdates can be used as self-separating catalysts in acetonitrile-mediated olefin epoxidations using hydrogen peroxide as oxidant.

Metal oxide-triazole hybrids as heterogeneous or reaction-induced self-separating catalysts

“…A comparison of the spectra for 1 and PS-(1-L-ct) in the 1000-1550 cm À1 range confirms that the organic ligand is retained in the yellow species isolated from the contact test, although some of the bands are shifted by up to 17 cm À1 when compared with the corresponding bands for 1. The behavior of 1 in liquid-phase catalytic olefin epoxidation parallels that recently reported for octamolybdate-based selfseparating catalysts of general formula [cation] 4 Mo 8 O 26 (cation = 1-hexyl-3-methylimidazolium, 1,2-dimethyl-3-hexylimidazolium, or 1-hexylpyridinium) [20]. Thus, with Cy as substrate, the octamolybdate salts dissolved in the presence of H 2 O 2 and CH 3 CN to give yellow homogeneous solutions, possibly containing oxodiperoxomolybdenum active species.…”

“…Herein, we describe an unprecedented behavior for the hybrid material [MoO 3 (trz) 0.5 ] when used in catalytic olefin epoxidation with H 2 O 2 as oxidant. In a manner similar to that reported with polyoxometalate salts [7,[10][11][12][13][14][15][16][17][18][19][20] a solid-liquid-solid phase transfer takes place, with spontaneous reassembly and selfprecipitation of the original molybdenum oxide-triazole solid upon completion of the reaction. Results with the molybdenum(VI) hybrid are compared with those for the corresponding tungsten (VI) compound, and the catalytic performances of both materials have been further examined for the oxidation of benzyl alcohol and benzaldehyde.…”

“…Since the publication of these two landmark papers, progress on self-precipitating transition metal catalysts has been slow. With some exceptions, such as a redox-switchable phase-tagged ruthenium-based catalyst [9], the solid-liquid-solid phase separation procedures are either reaction-controlled [10][11][12][13][14][15][16][17][18][19][20] or thermoregulated [21][22][23][24], and involve polyoxometalate salts of large organic cations [25].…”

Molecular Epoxidation Reactions Catalyzed by Rhenium, Molybdenum, and Iron Complexes

“…These systems are easily recyclable; however, the activity of the compounds in both epoxidation of olefins and oxidation of sulfides are quite low. The easy recyclability, combined with a promising activity (99% conversion of cis ‐cyclooctene after 1h, T = 60°C, 2 mol% catalyst concentration), has been demonstrated very recently with the use of an octamolybdate‐based “self‐separating” catalysts ([Mo 8 O 26 ] 4– with imidazolium counter cations . Our group has also focused on the in situ formation of POMs with Na 2 MoO 4 .…”

Amphiphilic Mesoporous Poly(Ionic Liquid) Immobilized Heteropolyanions Towards the Efficient Heterogeneous Epoxidation of Alkenes with Stoichiometric Hydrogen Peroxide

“…POMs have been studied extensively because of their high reactivity and selectivity, controllable structure, versatile acid/redox properties, strong persistence against oxidants, and environmental compatibility . Many POMs‐based catalysts have been developed for alkene epoxidation with H 2 O 2 . For example, Ti‐substituted phosphotungstate was active in the epoxidation of various alkenes .…”