The primary stages of polyoxomolybdate catalyzed cyclohexanone oxidation by hydrogen peroxide as investigated by in situ NMR. Substrate activation and evolution of the working catalyst

Abstract

The primary stages of polyoxomolybdate catalyzed cyclohexanone oxidation by hydrogen peroxide as investigated by in situ NMR.

Cyclohexanone Oxidation over H3PMo12O40 Heteropolyacid via Two Activation Modes Microwave Irradiation and Conventional Method

“…This has as for consequence the formation of peroxocomplexes highlighted by several techniques (X-ray diffraction, FTIR, and Raman spectroscopies). These complexes, with an oxidizing power stronger than that of H2O2, have been shown to be very active in several reactions [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]29]. In our case, we could admit that the reduced POM, from the first stage, oxidizes and simultaneously forms peroxocomplexes "peroxo-POMox".…”

Transition metal-substituted Keggin-type polyoxometalates as catalysts for adipic acid production

“…These peroxo species were reported by several authors as the active species in the formation of oxygenated compounds. They were evidenced by multinuclear NMR spectroscopies in the cases of H 3 [2,21].…”

“…In the second step, the addition of hydrogen peroxide led to a POM color change from blue to yellow that is attributed to the POMred oxidation. It was reported that in the presence of hydrogen peroxide, peroxo species such as {PO 4 [2,21]. This step can be explained by the following equation: During the 20 h of reaction, the peroxo-POM species will react with some products from the Eq.…”

“…In organic synthesis, H 2 O 2 is widely used in alkene epoxidation reactions [12,13,18] and Baeyer-Villiger oxidation reactions of cyclic ketones and aldehydes [37,38,40,41]. In the case of AA synthesis, H 2 O 2 was used in the presence of different catalysts such as µ 3 -oxo-bridged Co/ Mn cluster complexes CoMn 2 (O) [9], [Mn III T(p-Cl)PP] Cl [23], N-hydroxyphthalimide combined with Mn(acac) 2 or Co(OAc) 2 [19] [1]. In these processes, H 2 O 2 was added to the reaction mixture at the same time as the substrate (cyclohexene, cyclohexanone or cyclohexanol) and catalyst.…”

“…A redox reaction occurs in situ between Mo(VI) and M(II). On the other hand, in recent work, it has been shown that the proton presence in the POM allows the activation of cyclohexanone by keto-enolic tautomerization, before its oxidation into more oxygenated compounds [2].…”