Polyfunctional action of transition metal substituted heteropolytungstates in alkene epoxidation by molecular oxygen in the presence of aldehyde

Heterogeneous Wheel‐Shaped Cu20‐Polyoxotungstate [Cu20Cl(OH)24(H2O)12(P8W48O184)]25− Catalyst for Solvent‐Free Aerobic Oxidation of n‐Hexadecane

“…The conversion of nhexadecane increased with increase of catalyst amount, reached the maximum at 15 mg, and then decreased. In past reports, [33,34] it was shown that higher POM catalyst concentrations may also inhibit the autoxidation reaction. In line with the earlier observation of n-hexadecane oxidation, the oxidation of n-hexadecane was inferred to proceed through a free-radical autoxidation mechanism.…”

“…Control experiments indicate that in the absence of catalyst, the oxidation is extremely slow (Table 4, entry 1). It is known [11,15,17,33] that the oxidation of alkanes by transition metals generally involves the participation of free radicals.…”

Oxidation of methyl phenyl sulfide with molecular oxygen in the presence of isobutyraldehyde and transition metal monosubstituted heteropolytungstates

“…Alkene epoxidation by dioxygen in the presence of IBA, and various transition metal catalysts, including llPAs, has been proved to proceed via a radical chain mechanism [1,8,[11][12][13][14]. Note that superior catalytic properties of Co-containing compounds in the alkene-IBA co-oxidation have been reported previously [3,8,11,12].…”

“…Recently, very efficient catalytic systems for alkene epoxidation based on the combined use of dioxygen (oxidant), branched aliphatic aldehydes (reductant), and various transition metal complexes (catalyst) have been found [1][2][3][4][5][6][7][8]. Keggin-type substituted heteropolyanions (HPAs), PWnMO39 n" (PWnM) with M = Co(II), Mn(Il) and Fe(m) [3], M = Co(lI), Cu(H), Pd(I1), Ru(IV), Ti0V) and V(V) [7,8], PMo6V60409- [4] and PWgO37Fe2Ni(OAc)3 ~~ [5] were found to mediate this reaction. The oxidation of kctones, alcohols, lactams, aromatics and alkanes has also been reported in several papers [1, 6 and [6,9].…”

“…Earlier cooxidation of thioethers with acetaldehyde has been found to proceed efficiently both without a catalyst and in the presence of Co(if) stearate at elevated temperature and pressure [10]. Recently we have studied the mechanism of alkene epoxidation by dioxygen in the presence of isobutyraldehyde 0BA) and transition-metal-substituted HPAs [8] as well as different type cobalt-containing compounds [11,12]. Here we report the study of the catalytic properties of PWuM with M = Co(l/), Cu(ll-), Pd(ll), RuOV), TiOV), and V(V) in the oxidation of thioethers by the dioxygen/IBA system at ambient conditions using methyl phenyl sulfide as a model substrate, and provide some data which allow to propose a reaction mechanism.…”