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Leiden, Netherlands

Saisaha P.,University of Groningen | De Boer J.W.,Catexel BV | Browne W.R.,University of Groningen
Chemical Society Reviews | Year: 2013

The development of new catalytic systems for cis-dihydroxylation and epoxidation of alkenes, based on atom economic and environmentally friendly concepts, is a major contemporary challenge. In recent years, several systems based on manganese catalysts using H2O2 as the terminal oxidant have been developed. In this review, selected homogeneous manganese catalytic systems, including 'ligand free' and pyridyl amine ligand based systems, that have been applied to alkene oxidation will be discussed with a strong focus on the mechanistic studies that have been carried out. This journal is © The Royal Society of Chemistry. Source


Hage R.,Catexel BV | de Boer J.W.,Catexel BV | Gaulard F.,Catexel BV | Maaijen K.,Catexel BV
Advances in Inorganic Chemistry | Year: 2013

Oxidation catalysts play an important role in a variety of industrial processes. These include stain bleaching in detergent applications, the bleaching of raw cotton and wood pulp, defined chemical transformations in the bulk chemical industry, and the drying of alkyd-based paints. In order to lower the environmental footprint of these processes, the use of highly atom efficient oxidants such as dioxygen or hydrogen peroxide and the use of catalysts based on environmentally benign metals such as manganese or iron are preferred. The mechanistic studies on Mn-tacn- and Fe-bispidon-based catalysts (tacn: 1,4,7-triazacyclononane; bispidon: 3,7-diazabicyclo[3.3.1]nonan-9-one) as well as their various oxidative application areas are reviewed in more detail, including discussion of the similarities of the fundamental chemistry involved in these different fields of application. © 2013 Elsevier Inc. Source


De Boer J.W.,Catexel BV | Wesenhagen P.V.,Catexel BV | Wenker E.C.M.,Catexel BV | Maaijen K.,Catexel BV | And 3 more authors.
European Journal of Inorganic Chemistry | Year: 2013

Paint formulations, based either on organic solvents or on water, often contain alkyd resins that depend on catalysts for their oxidative curing. Cobalt carboxylates are the most widely used to date, but the use of these compounds is under pressure because classification as carcinogens under the REACh system is probable, and as a consequence there is great interest in the development of alternative driers to cobalt-based ones. A variety of manganese and iron carboxylates have been studied as paint drying catalysts in the last two decades, but these often show drawbacks with respect to activity, level of application, colour of the paint drier or cost in use. More recently, several reports on active manganese and iron paint driers containing polydentate ligands have been published. In particular, one iron-based catalyst, identified originally for stain bleaching in laundry cleaning, shows good paint drying activity at very low dosage levels, outperforming cobalt carboxylates in a wide range of applications. Paints containing alkyd resins need catalysts for oxidative curing. Because of the probable reclassification of the widely used cobalt carboxylates as carcinogens there is interest in alternative alkyd paint drying catalysts. Various manganese and iron paint driers with polydentate ligands have recently been reported; a particular iron-based catalyst shows good paint drying activity at low dosage. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Saisaha P.,University of Groningen | Buettner L.,University of Groningen | Van Der Meer M.,University of Groningen | Hage R.,Catexel BV | And 3 more authors.
Advanced Synthesis and Catalysis | Year: 2013

The manganese-containing catalytic system [MnIV,IV 2O3(tmtacn)2]2+ (1)/carboxylic acid (where tmtacn=N,N′,N′′-trimethyl-1,4,7-triazacyclononane), initially identified for the cis-dihydroxylation and epoxidation of alkenes, is applied for a wide range of oxidative transformations, including oxidation of alkanes, alcohols and aldehydes employing H2O2 as oxidant. The substrate classes examined include primary and secondary aliphatic and aromatic alcohols, aldehydes, and alkenes. The emphasis is not primarily on identifying optimum conditions for each individual substrate, but understanding the various factors that affect the reactivity of the Mn-tmtacn catalytic system and to explore which functional groups are oxidised preferentially. This catalytic system, of which the reactivity can be tuned by variation of the carboxylato ligands of the in situ formed [MnIII,III 2(O)(RCO2)2(tmtacn)2]2+ dimers, employs H2O2 in a highly atom efficient manner. In addition, several substrates containing more than one oxidation sensitive group could be oxidised selectively, in certain cases even in the absence of protecting groups. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Abdolahzadeh S.,University of Groningen | Boyle N.M.,University of Groningen | Draksharapu A.,University of Groningen | Dennis A.C.,Andor Technology | And 3 more authors.
Analyst | Year: 2013

The application of drop coating deposition Raman (DCDR) spectroscopy to the field of reaction progress monitoring is addressed in this contribution. Although, DCDR spectroscopy has seen recent application in the study of biological fluids, its application in other areas has not yet been explored. Here we apply the technique to the catalysed oxidation of alkenes to epoxides in aqueous solutions at concentrations <10 mM. The effect of surface characteristics, background interferences, homogeneity of distribution of analytes, drying time, as well as instrumental limits of detection and calibration are discussed. We demonstrate that reproducible spectra can be obtained routinely, with relatively little variance, with short acquisition times and samples volumes of 2-10 μl and as little as 1 μg of analyte. The utility of the technique compared with online reaction monitoring by 1H NMR and Raman spectroscopy is demonstrated in the excellent correlation between data obtained off and on-line. This journal is © The Royal Society of Chemistry 2013. Source

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