Search results for "Benzoin"

Allergic contact dermatitis from anthrarobin.

1995

Dalton communication. Crystal structure and oxo-transfer properties of [NH4]2[WVIO2{O2CC(S)Ph2}2]

1994

The complex [NH4]2[WVIO2{O2CC(S)Ph2}2] is the first example of a non-dithiolene tungsten complex capable of oxidising benzoin to benzil in methanol; the reduced complex product formed, presumably a monomeric WVIO species, was reoxidised with nitrate ions, regenerating the starting WVIO2 complex which then acts as a true homogeneous catalyst.

Dioxomolybdenum(VI) complexes with tri- and tetradentate aminobis(phenolate)s

2005

Abstract The reactions of tridentate ligands, bis(2-hydroxy-3,5-dimethylbenzyl)methylamine (H2ONOMe) and bis(2-hydroxy-3-tert-butyl-5-methylbenzyl)methylamine (H2ONOtBu) with [MoO2(acac)2] (1) in methanol lead to the precipitation of monomeric dioxomolybdenum(VI) complexes [MoO2(ONOMe)(MeOH)] · MeOH (2a) and [MoO2(ONOtBu)(MeOH)] · MeOH (2b), respectively. Identical reactions in acetonitrile provide dimeric complexes [Mo2O2(μ-O)2(ONOMe)2] (3a) and [Mo2O2(μ-O)2(ONOtBu)2] (3b). The reactions of 1 with tetradentate ligands, N,N′-bis(2-hydroxy-3,5-dimethylbenzyl)-N,N′-dimethylethane-1,2-diamine (H2ONNOMe) and N,N′-bis(2-hydroxy-3,5-di-tert-butylbenzyl)-N,N′-dimethylethane-1,2-diamine (H2ONNOtBu)…

Azolium and acetate ions in DMF: Formation of free N-heterocyclic carbene. A voltammetric analysis

2016

In order to reveal the possible formation of free N-heterocyclic carbene (NHC) in DMF-azolium and acetate solutions, the proton exchange equilibrium between azolium cations and CH3COO− was investigated (by cyclic voltammetry) by adding CH3COOH or tetrabutylammonium acetate to DMF solutions of imidazolium or thiazolium salts of different acidity.The voltammetric analysis confirms that the deprotonation of the azolium cation by CH3COO− (with the formation of free NHC) is significant in the case of the more acidic thiazolium cations, while it is not effective with the less acidic imidazolium ones.Accordingly, the NHC-catalyzed benzoin condensation was carried out in DMF solutions of azolium sa…

Degradation of dimeric lignin model compounds by aerobic bacteria isolated from the hindgut of xylophagous termites.

1997

The capability of the intestinal flora from the gut of xylophagous termites of degrading lignin model compounds was investigated. Different dimeric lignin model compounds-degrading bacteria were obtained from the hindgut flora of Mastotermes darwiniensis FROGGATT, Reticulitermes santonensis FEYTAUD, Nasutitermes nigriceps HALDEMAN and Zootermopsis angusticollis HAGEN. In the presence of oxygen dimeric model compounds were degraded by all isolates. This indicates that the hindgut flora of termites is basically able to produce substrate for their host from aromatic extractives of wood.

Oxygen atom transfer reaction involving oxomolybdenum complexes with sterically bulky thiocarboxylate ligands and biochemical interesting substrates …

1999

Abstract Oxidation–reduction reactions of substrates in systems containing the complex [Mo VI O 2 (O 2 CC(S)CH 3 Ph) 2 ] 2− in methanol have been investigated as models of oxo-transfer reactions. At neutral pH, the [Mo VI O 2 (O 2 CC(S)CH 3 Ph) 2 ] 2− reacts with Me 2 PhP or n -butanethiol to yield a [Mo IV O(O 2 CC(S)CH 3 Ph) 2 ] 2− species and Me 2 PhPO or disulfide, respectively. The Mo IV O complex reduces a variety of substrates XO = Me 2 SO and pyridine N-oxide conducing formation of X = Me 2 S and pyridine. The occurrence of these reactions produces a catalytic system Me 2 PhP + XO → Me 2 PhPO + X and 2BuSH + XO → [BuS] 2  + X + H 2 O. In this work we have also included the study of …

Organocatalytic Enantioselective Synthesis of α-Hydroxyketones through a Friedel−Crafts Reaction of Naphthols and Activated Phenols with Aryl- and Al…

2016

[EN] An efficient organocatalytic asymmetric synthesis of alpha-hydroxyketones has been developed. Quinine-derived thiourea catalyzed the enantioselective Friedel Crafts alkylation of naphthols and activated phenols with aryl- and alkylglyoxal hydrates, providing the corresponding chiral alpha-hydroxyketones with high yields (up to 97%) and excellent enantioselectivities (up to 99% ee).

Zirconium oxocluster/polymer hybrid nanoparticles prepared by photoactivated miniemulsion copolymerization

2017

The photoactivated free radical miniemulsion copolymerization of methyl methacrylate (MMA) and the zirconium oxocluster Zr4O2(methacrylate) 12 is used as an effective and fast preparation method for polymer/inorganic hybrid nanoparticles. The oxoclusters, covalently anchored to the polymer network, act as metal-organic cross-linkers, thus improving the thermomechanical properties of the resulting hybrid nanoparticles. Benzoin carbonyl organic compounds were used as photoinitiators. The obtained materials are compared in terms of cross-linking, effectiveness of cluster incorporation, and size distribution with the analogous nanoparticles produced by using conventional thermally induced free …

Polymer-supported molybdenyl thioglycolate as oxygen atom transfer reagent

2000

Abstract Oxo-transfer reactions of a variety of substrates in DMF or methanol using polymer-supported molybdenyl thioglycolate (PSMT) have been investigated. The clean oxidation of Me 2 PhP, n -butanethiol or benzoin to yield Me 2 PhPO, disulfide or benzil, respectively, occurs in high yield. In the presence of air or pyridine N-oxide, a catalytic cycle is accomplished which goes on until the completion of the substrate.

Dioxidomolybdenum(VI) and -tungsten(VI) complexes with tripodal amino bisphenolate ligands as epoxidation and oxo-transfer catalysts

2017

The molybdenum(VI) and tungsten(VI) complexes [MO2(L)] (M = Mo (1), W (2), H2L = bis(2-hydroxy-3,5-di-tert-butybenzyl)morpholinylethylamine) were synthesized and the complexes were used to catalyze oxotransfer reactions, viz. sulfoxidation, epoxidation and benzoin oxidation. For comparison, the same reactions were catalyzed using the known complexes [MO2(L′)] (M = Mo (3), W (4), H2L′ = bis(2-hydroxy-3,5-di-tert-butybenzyl)ethanolamine) and [MO2(L″)] (M = Mo (5), W (6), H2L″ = bis(2-hydroxy-3,5-di-tert-butybenzyl)diethyleneglycolamine). The oxo atom transfer activity between DMSO and benzoin at 120 °C was identical for all studied catalysts. Reasonable catalytic activity was observed for sul…