Nafion®-supported vanadium oxidation catalysts: redox versus acid-catalysed ring opening of 2-substituted cycloalkanones by dioxygen

K-10 montmorillonite: An efficient and reusable catalyst for the aerobic CC bond cleavage of α-substituted ketones

“…Nevertheless, a moderate yield is obtained with K-10MT if no acid is added in the reaction medium indicating that the intrinsic acidity of the clay is not sufficient to induce appreciable conversion of the substrate. The improvement of the catalytic activity with the addition of acids is well known [6,7,35,36]. Several reasons have been proposed: (i) the oxidation reaction proceeds first via the formation of the enol tautomer from the cyclic ketone, which is enhanced in the presence of protons [6,7,35,36], (ii) peracetic acid could be generated in situ from acetic acid, the former acting as an oxidant [36] and (iii) the protonation of the cyclohexanone may facilitate its dissolution as far as water is used as the solvent [36] (the solubility of 2-methylcyclohexanone is about 2 g per 100 mL at 20 • C [37] 40 ]·aq (n = 1 and 2) polyoxometalates: the highest conversion was observed for an equivolumetric mixture of water and acetic acid [36].…”

“…Efforts have therefore been made to develop homogeneous catalysts [6] and eco-friendly heterogeneous catalysts for the synthesis of industrially important ketoacids. In this context, we have demonstrated that Nafion ® supported vanadium oxo species [7] catalyze efficiently the aerobic cleavage of C C bonds in some ␣-ketols with good yields and can be recycled.…”

Oxidative C−C Cleavage of Ketols over Vanadium–Carbon Catalysts

“…Typical catalysts foro xidative CÀCc leavage with O 2 are based on Ru, [6][7][8][9][10] Mn, [11] Cu, [12][13][14] and V. [10,13,[15][16][17][18][19][20][21][22] Ru and Mn catalysts can convert aromatic vicinald iol to aldehydes in good yields and they are less effective for aliphatic substrates, especially under neutralo ra cidic conditions. Substrates for Cu-catalyzed CÀCo xidation are also aromatic compounds, typicallyt hose with benzoyl groups.H owever,h omogeneous vanadium catalysts are active in the oxidative CÀCc leavage of aliphatic ketols such as 2-hydroxycyclohexanone [10,15,16] and sugars [17][18][19][20][21][22] to adipic acid and formic acid, respectively (Scheme 1). As re-lated systems, the oxidation of catechols [23,24] and lignin model compounds [25][26][27][28] with homogeneous vanadium catalysts have also been investigated intensively.T he mosti nvestigated Vbased catalyst in the oxidative CÀCc leavage of ketols is the Keggin-type polyoxometalate H 3 + n PV n Mo 12Àn O 40 (PVMo).…”

From polyoxometalates to polyoxoperoxometalates and back again; potential applications

“…These oxidative systems can be considered as models of dioxygenases [17,68,97,102]. The reactions are of practical interest and were traditionally achieved using stoichiometric oxidants such as periodates or lead tetraacetate causing the already-mentioned pollution problems which can be avoided by these HPA catalysts as well as by simple precursors [17,[102][103][104][105]. The catalytic behaviour of such oxidation catalysts might be promising for oxidative cleavage.…”

“…Nafion ® -supported vanadium catalysts based on the [VO 2 ] + /[VO] 2+ couple [105] or on modified HPA-n species are fairly active for cyclohexane oxidation: they give oxygenated products (aldehyde or keto acids, ␣, -diacids, alcohols, ketones, lactones). High yields and conversions have been obtained [17]; thus they compete with the recently proposed gold-based systems?…”