Olefin epoxidation in solventless conditions and apolar media catalysed by specialised oxodiperoxomolybdenum complexes
摘要:
The epoxidation of olefin substrates, in both apolar organic media and under solventless conditions, with aqueous hydrogen peroxide and catalysed by molybdenum complexes has been investigated. The catalysts compounds employed were the oxodiperoxomolybdenum complexes of several pyridine, 2,2'-bipyridine and pyrazole ligands with apolar functions (alkyl chains, alkyl-trimethylsilyl groups and polydimethylsiloxanyl polymer), which showed enhanced solubility in relatively apolar organic media. Both the isolated complexes and in situ preparations were catalytically active. The solubility of the new catalyst complexes appears to facilitate the catalytic activity in these systems, since activity was not observed for the analogous, insoluble complexes of unfunctionalised ligands. In these systems, the oxidant, aqueous hydrogen peroxide, forms a separate phase and the catalyst resides in the organic phase. From a green chemistry and economic perspective the elimination of organic solvents and co-catalysts from a reaction system would present advantages and, consequently, the epoxidation reaction was also investigated under solventless conditions. The 3-hexyl-5-methylpyrazole and 3-hexyl-5-heptylpyrazole complexes were found to show heightened activities, the latter being particularly efficient in these conditions, whilst bipyridines apparently inhibit the epoxidation. In addition, the mechanism of the epoxidation reaction was studied through DFT calculations for the model olefin substrate ethylene with the oxodiperoxomolybdenum complex of 3-hexyl-5-heptylpyrazole. The oxo-transfer reaction occurred by interaction of the ethylene with the peroxo ligand via the spirocyclic transition state proposed by Sharpless. (C) 2011 Elsevier B.V. All rights reserved.
Direct C-4-selective addition of pyridine across alkenes and alkynes is achieved for the first time by nickel/Lewisacid cooperative catalysis with an N-heterocyclic carbene ligand. A variety of substituents on both alkenes and pyridine are tolerated to give linear 4-alkylpyridines in modest to good yields. The addition across styrene, on the other hand, gives branched 4-alkylpyridines. A single example
Biphasic catalytic olefinepoxidation systems consisting of oxodiperoxomolybdenum catalysts in 1-n-alkyl-3-methylimidazolium hexafluorophosphate ionic liquid (IL) media with aqueous hydrogenperoxide oxidant were optimised by tuning the molecular structure of the IL and employing N-heterocyclic donor base additives to inhibit hydrolysis and enhance the activity of the catalyst. The latter study was
4-ALKYL SUBSTITUTED PYRIDINES AS ODIFEROUS SUBSTANCES
申请人:Oertling Heiko
公开号:US20100130624A1
公开(公告)日:2010-05-27
The present invention primarily concerns certain 4-alkyl pyridines of the following formula (I),
wherein R is C
8
-C
12
alkyl, odiferous substance mixtures and aromatic substance mixtures containing these 4-alkyl pyridines, the respective uses thereof as an odiferous or aromatic substance (mixture) and corresponding perfumed products.
Functionalized Membranes for Photocatalytic Hydrogen Production
作者:Stefan Troppmann、Burkhard König
DOI:10.1002/chem.201404480
日期:2014.11.3
under optimized conditions in purely aqueous solution. Superior photocatalytic activity in fluid membranes indicates that mobility and dynamic reorganization of catalytic subunits in the membrane promote the visible‐light‐driven hydrogenproduction. The functionalizedmembranes represent nanostructured assemblies for hydrogenproduction in aqueous solution mimicking natural photosynthesis.
Die vorliegende Erfindung betrifft primär bestimmte 4-Alkylpyridine der nachfolgenden Formel (I), Riechstoff- und Aromastoffmischungen umfassend diese 4-Alkylpyridine, deren jeweilige Verwendung als Riech- oder Aromastoff(mischung) und entsprechende parfümierte Produkte.
Besonders bevorzugt sind die 4-n-Alkylpyridine, deren Alkylrest 8-12 C-Atome enthält.