Epoxidation of tertiary allylic alcohols and subsequent isomerization of tertiary epoxy-alcohols : a comparison of some catalytic systems for demanding ketonization processes

Another Example of the Instability of a Keggin‐Type Heteropolyanion in the Presence of Aqueous Hydrogen Peroxide: From [AsW12O40]3– to Low‐Nuclearity Oxoperoxotungstates – Crystal Structure of [(nHex)4N]3[AsO4{W2O2(μ‐O2)2(O2)2}2]

“…[13,30] Figure 3 shows that half of the peroxide oxygen is transferred to the olefinic substrate at room temperature, a result which differs from that of the MTO/H 2 O 2 systems. [29,53] Comparative experiments with "CH 3 ReO 3 + 2H 2 O 2 /solvent" show complete transfer of the peroxide oxygen. 2-complex are fluxional.…”

“…They transfer active oxygen to (R)-(+)-limonene to mostly give the monoepoxides, which are known to be acid-sensitive. [55][56][57] Complete optimisation must consider the effects of the organic solvent, the nature of Q + , the assembling ligand X and the anionic species (Cl -, Br -, HSO 4 -, etc. ), the pH of the aqueous phase, the presence of Na + Cl -and the W/X/Q + ratios, and these factors have been analysed in detail by several groups.…”

“…[6,25] Although it was formerly accepted that the O-O bond lengths are fairly constant and do not depend on the nature of the metal ligands, we were interested in a systematic study of the heteroligand effect. This is of major importance for catalysis in homogeneous [6,29] or two-phase-medium [6,9,13,22,23,30,31] conditions, for grafting onto (or inserting in) polymeric supports [6,30,[32][33][34][35][36][37][38] or for the comprehensive study of the synthesis of transition-metal-containing mesostructured materials from peroxo species. [39,40] We report here the synthesis and structural characterisation of [(nHex) 4 …”

From polyoxometalates to polyoxoperoxometalates and back again; potential applications

“…Some anionic complexes with the dimeric moiety {M 2 O 2 (-O 2 ) 2 (O 2 ) 2 }, as a principal building block are better, for the transfer of active oxygen, than mononuclear species which are much less active. The combination of these anions with appropriate cations is claimed to be as active and selective as the two-phase systems: "MeReO 3 (MTO)/H 2 O 2 -H 2 O/organic solvent" [17,[34][35][36][37] particularly effective for the epoxidation of acid-sensitive epoxides. The addition of "proton sponges" (e.g.…”

“…The instability of another Keggintype heteropolyanion in the presence of aqueous hydrogen peroxide was also reported recently [38] [20][21][22]39,40], though anhydrous mono-and dinuclear tungsten peroxo species may contribute. Subsequent reactions to produce diols from epoxides and even carbon-carbon bond cleavage can be suppressed, resulting in a very high selectivity for epoxidation at room temperature [34,37,38] [15,16], (M = Mo or W) indicate that the two catalysis systems involve common oxoperoxo anions, despite the fact that each group patented its particular set of catalyst precursors as novel chemistry. These systems, nevertheless, can differ in the concentration ratios of the neutral and anionic species.…”