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ResearchMolecular Inorganic Chemistry - Browne group


SOLCAT - Shedding light on oxidation catalysis

The SOLCAT project is funded by the ERC through a Starting Investigator (Consolidator) Grant awarded by the Physical Sciences and Engineering section in June 2011. The project starting in December 2011 with the first student Davide Angelone joining the Browne research group to undertake a PhD. The second PhD student to join the project (April 2012) was Francesco Mecozzi and (December 2012) Duenpen Unjareon. The final PhD student funded by the program is Sandeep Kumar (January 2014). Dr Nicola Boyle joined the project in February 2013 as a Postdoctoral researcher.

Project output

Strand 1 Manganaese catalyzed selective oxidations

(1) A simple, high yielding catalytic method for the multigram scale selective epoxidation of electron-rich alkenes using near-stoichiometric H2O2 under ambient conditions is reported. The system consists of a Mn(II) salt (<0.01 mol %), pyridine-2-carboxylic acid (<0.5 mol %), and substoichiometric butanedione. High TON (up to 300 000) and TOF (up to 40 s–1) can be achieved for a wide range of substrates with good to excellent selectivity, remarkable functional group tolerance, and a wide solvent scope. It is shown that the formation of 3-hydroperoxy-3-hydroxybutan-2-one from butanedione, and H2O2 in situ, is central to the activity observed.

J. Dong, P. Saisaha, T. M. Meinds, P. L. Alsters, E. Ijpeij, R. P. van Summeren, B. Mao, M. Fañanás-Mastral, J. W. de Boer, R. Hage, B. L. Feringa, W. R. Browne, "Oxidation of alkenes with H2O2 by an in situ prepared Mn(II)/pyridine-2-carboxylic acid catalyst and the role of ketones in activating H2O2" ACS Catalysis, 2012, 2, 1087–1096,

(2) An efficient and simple method for selective oxidation of secondary alcohols and oxidation of alkanes to ketones is reported. An in situ prepared catalyst is employed based on manganese(II) salts, pyridine-2-carboxylic acid and butanedione, which provides good to excellent conversions and yields with high turnover numbers (up to 10,000) with H2O2 as oxidant at ambient temperatures. In substrates bearing multiple alcohol groups, secondary alcohols are converted to ketones selectively and in general, benzyl C-H oxidation proceeds in preference to aliphatic C-H oxidation

J. Dong, D. Unjaroen, F. Meccozi, E. C. Harvey, P. Saisaha, D. Pijper, J. W. de Boer, P. Alsters, B L. Feringa and W. R. Browne "Manganese Catalyzed Selective Oxidation of Aliphatic C-H groups and Secondary Alcohols to Ketones with Hydrogen Peroxide" ChemSusChem, 2013, in press

(3) The 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 and the activation of C-H bonds alkanes is examined as well. 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 carboxylate 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.

P. Saisaha, L. Buettner, M. van der Meer, R. Hage, B. L. Feringa, W. R. Browne, J. W. de Boer, " Selective catalytic oxidation of alcohols, aldehydes, alkanes and alkenes employing manganese catalysts and hydrogen peroxide" Adv. Synth. Cat. 2013, in press

Strand 2 Mechanistic studies on Manganese catalyzed oxidation catalysis

(4) 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.

P. Saisaha, J. W. de Boer, W. R. Browne, "Mechanisms in manganese catalysed oxidation of alkenes with H2O2" Chem. Soc. Rev., 2013, 42, 2059-2074.

Strand 3 Palladium catalyzed Wacker oxidation

(5) The Pd(II)-catalysed anti-Markovnikov oxidation of allylic esters to aldehydes at room temperature provides a viable alternative to valuable cross aldol products. High regioselectivity towards the aldehyde product was achieved using the ester protecting group for the allylic alcohol. Remarkably, rapid isomerization, catalysed by palladium, between linear and branched allylic ester regioisomers, together with the much higher rate of oxidation of the branched isomer, results in the same aldehyde product forming selectively both form the linear and branched allylic esters.

J. J. Dong, M. Fañanás-Mastral, P. L. Alsters, W. R. Browne, B. L. Feringa, "Pd-catalysed Selective Anti-Markovnikov Oxidation of Allylic Esters " Angew. Chem. 2013 in press

Strand 4 Flow chemistry

In progress

Strand 5 HTS catalyst discovery

In progress

Laatst gewijzigd:28 juli 2017 11:12