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Citation
Tags
HERO ID
7779690
Reference Type
Journal Article
Title
The unexpected role of pyridine-2-carboxylic acid in manganese based oxidation catalysis with pyridin-2-yl based ligands
Author(s)
Pijper, D; Saisaha, P; de Boer, JW; Hoen, R; Smit, C; Meetsma, A; Hage, R; van Summeren, RP; Alsters, PL; Feringa, BL; Browne, WR
Year
2010
Is Peer Reviewed?
Yes
Journal
Dalton Transactions (Online)
ISSN:
1477-9234
Volume
39
Issue
43
Page Numbers
10375-10381
Language
English
PMID
20886164
DOI
10.1039/c0dt00452a
Web of Science Id
WOS:000283601900005
Abstract
A number of manganese-based catalysts employing ligands whose structures incorporate pyridyl groups have been reported previously to achieve both high turnover numbers and selectivity in the oxidation of alkenes and alcohols, using H(2)O(2) as terminal oxidant. Here we report our recent finding that these ligands decompose in situ to pyridine-2-carboxylic acid and its derivatives, in the presence of a manganese source, H(2)O(2) and a base. Importantly, the decomposition occurs prior to the onset of catalysed oxidation of organic substrates. It is found that the pyridine-2-carboxylic acid formed, together with a manganese source, provides for the observed catalytic activity. The degradation of this series of pyridyl ligands to pyridine-2-carboxylic acid under reaction conditions is demonstrated by (1)H NMR spectroscopy. In all cases the activity and selectivity of the manganese/pyridyl containing ligand systems are identical to that observed with the corresponding number of equivalents of pyridine-2-carboxylic acid; except that, when pyridine-2-carboxylic acid is used directly, a lag phase is not observed and the efficiency in terms of the number of equivalents of H(2)O(2) required decreases from 6-8 equiv. with the pyridin-2-yl based ligands to 1-1.5 equiv. with pyridine-2-carboxylic acid.
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