- Synthesis, Characterization and Catalytic Activity of a Tungsten(VI) Amino Triphenolate Complex
-
Abstract: Synthesis, characterization and catalytic activity of a novel tungsten(VI) amino triphenolate complex have been investigated. In particular, a tungsten(VI) amino triphenolate complex has been synthesized and tested in the oxidation of sulfides and cyclooctene, using hydrogen peroxide as terminal oxidant. The catalyst has proved to be air and water tolerant, also showing a good efficiency in terms of yields and selectivity. Moreover, an upgrade of our previous ligand synthesis is herein reported. The new developed procedure allows to obtain the triphenolamine in large scale without the use of chromatography for the intermediates purification. Graphical Abstract: [Figure not available: see fulltext.].
- Badetti, Elena,Bonetto, Alessandro,Romano, Francesco,Marchiò, Luciano,Zonta, Cristiano,Licini, Giulia
-
p. 2313 - 2318
(2017/08/22)
-
- Sulfoxidation with hydrogen peroxide catalyzed by [SeO 4{WO(O2)2}2]2-
-
The selenium-containing dinuclear peroxotungstate, [(n-C4H 9)4N]2[SeO4{WO(O2) 2}2] (I), acts as a homogeneous catalyst for the selective oxidation of various kinds of cyclic mono- and disulfides with 30% aqueous H2O2. The cyclic disulfides were selectively oxidized to the corresponding monosulfoxides with one equivalent of H2O 2 with respect to the sulfides. In the presence of two equivalents of H2O2, the oxidation of dibenzothiophene gave the corresponding sulfone in 98% yield under the mild conditions. The negative Hammett ρ value (-0.62) for the competitive oxidation of p-substituted thioanisoles and the low XSO (XSO = (nucleophilic oxidation)/(total oxidation)) value of 0.14 for the I-catalyzed oxidation of thianthrene 5-oxide (SSO) revealed that I is a strong electrophilic oxidant. The reactivities of the di- and tetranuclear peroxotungstates with XO 4n- ligands (X = Se(vi), As(v), P(v), S(vi), and Si(iv)) were strongly dependent on the kinds of hetero atoms. The reaction rates for the sulfoxidation decreased with an increase in the XSO values and a peroxotungstate with a stronger electrophilicity was more active for the sulfoxidation. The kinetic and mechanistic investigations showed that the electrophilic attack of the peroxo oxygen at the sulfur atom is a key step in the sulfoxidation. The computational investigation supported the high chemoselectivitiy for the sulfoxidation of diallyl sulfide.
- Kamata, Keigo,Hirano, Tomohisa,Ishimoto, Ryo,Mizuno, Noritaka
-
experimental part
p. 5509 - 5518
(2010/08/04)
-
- Selective oxidation of sulfides to sulfoxides catalyzed by ruthenium (III) meso-tetraphenylporphyrin chloride in the presence of molecular oxygen
-
Highly efficient selective oxidation of sulfides to sulfoxides by molecular oxygen catalyzed by ruthenium (III) meso-tetraphenylporphyrin chloride (Ru(TPP)Cl) with isobutyraldehyde as oxygen acceptor has been reported. In large-scale experiment of thioanisole oxidation, the isolated yield of sulfoxide of 92% was obtained and the turnover number reached up to 92,000.
- Zhou, Xian-Tai,Ji, Hong-Bing,Cheng, Zhao,Xu, Jian-Chang,Pei, Li-Xia,Wang, Le-Fu
-
p. 4650 - 4653
(2008/02/09)
-
- Oxygen Exchange between Sulphoxides and Sulphides. Part 3. The HCl-Catalysed Reduction of Aryl Methyl Sulphoxides by Dialkyl Sulphides in Aqueous Methanol
-
Dialkyl sulphides reduce aryl methyl sulphoxides in aqueous methanol in the presence of ca. 4 mol dm-3 HCl.Ring substitution in phenyl methyl sulphoxides moderately affects their reactivity towards dibutyl sulphide, the overall effect resulting in a Hammett ρ value of -1.6.This parameter is a measure of the effect of structural changes on a protonation pre-equilibrium, the formation of chlorosulphonium ion, and its subsequent partitioning between reduction and return to reactants by the action of water.Changing the alkyl moiety of the sulphides induces moderate reactivity changes suggesting a compensation of opposite polar and steric effects.Sulphoxides with electron-releasing groups display the highest selectivity towards dialkyl sulphides.When a large concentration of sulphide is used, both racemization of chiral sulphoxide and 18O exchange with the aqueous solvent are suppressed and this suggests that the species ArR1SCl+ is a common intermediate for these processes and for the reduction reaction.These and other kinetic findings indicate that the reduction step involves the displacement at the ArR1SCl+ chlorine of a sulphide by a sulphide molecule rather than by chloride ion and rules out, for the racemization too, the hypothesis involving a free halogen intermediate.
- Miotti, Umberto
-
p. 617 - 622
(2007/10/02)
-