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- ItemSelective Wacker type oxidation of a macrocyclic diene to the corresponding monounsaturated ketone used as fragrance(Cambridge : RSC, 2019) Brunzel, Tom; Heppekausen, Johannes; Panten, Johannes; Köckritz, AngelaA selective reaction method for the efficient conversion of an isomeric mixture of 1,9-cyclohexadecadiene (1,9-CHDD) to the corresponding monounsaturated cyclohexadec-8-en-1-one (8-CHD) is described. 8-CHD was synthesized via Wacker type oxidation at room temperature using a highly electrophilic in situ formed dicationic palladium species. Isomerisation of the diene and over-oxidation of the substrate could be nearly suppressed by suitable reaction control, which has a positive effect on selectivity. The utilization of molecular oxygen as a green oxidant and environmentally benign iron(iii) salts as co-catalysts was successfully applied. This reaction strategy is promising to overcome the low overall reactivity of internal olefins in Wacker type oxidations. In addition, larger scale experiments showed further potential for industrial application. This journal is © 2019 The Royal Society of Chemistry.
- ItemSelective reductive amination of aldehydes from nitro compounds catalyzed by molybdenum sulfide clusters(Cambridge : RSC, 2017) Pedrajas, E.; Sorribes, I.; Junge, K.; Beller, M.; Llusar, R.Secondary amines are selectively obtained from low value starting materials using hydrogen and a non-noble metal-based catalyst. The reductive amination of aldehydes from nitroarenes or nitroalkanes is efficiently catalyzed by a well-defined diamino molybdenum sulfide cluster in a one-pot homogeneous reaction. The integrity of the molecular cluster catalyst is preserved along the process.
- ItemEarth-abundant photocatalytic systems for the visible-light-driven reduction of CO2 to CO(Cambridge : RSC, 2017) Rosas-Hernández, Alonso; Steinlechner, Christoph; Junge, Henrik; Beller, MatthiasHerein, we report a highly selective photocatalytic system, based on an in situ copper photosensitizer and an iron catalyst, for the reduction of CO2 to CO. Turnover numbers (TON) up to 487 (5 h) with selectivities up to 99% and ΦCO = 13.3% were observed. Stern-Volmer analysis allowed us to establish a reductive quenching mechanism between the Cu PS and electron donor.
- ItemSynthesis of pharmaceutical drugs from cardanol derived from cashew nut shell liquid(Cambridge : RSC, 2019) Shi, Yiping; Kamer, Paul C.J.; Cole-Hamilton, David J.Cardanol from cashew nut shell liquid extracted from cashew nut shells was successfully converted into various useful pharmaceutical drugs, such as norfenefrine, rac-phenylephrine, etilefrine and fenoprofene. 3-Vinylphenol, the key intermediate for the synthesis of these drugs, was synthesised from cardanol by ethenolysis to 3-non-8-enylphenol followed by isomerising ethenolysis. The metathesis reaction worked very well using DCM, but the greener solvent, 2-methyl tetrahydrofuran, also gave very similar results. Hydroxyamination of 3-vinylphenol with an iron porphyrin catalyst afforded norfenefrine in over 70% yield. Methylation and ethylation of norfenefrine afforded rac-phenylephrine and etilefrine respectively. A sequence of C-O coupling, isomerising metathesis and selective methoxycarbonylation afforded fenoprofene in good yield. A comparison of the routes described in this paper with some standard literature syntheses of 3-vinylphenol and of the drug molecules shows significant environmental advantages in terms of precursors, yields, number of steps, conditions and the use of catalysts. The Atom Economy of our processes is generally similar or significantly superior to those of the literature processes mainly because the side products produced during synthesis of 3-vinylphenol (1-octeme, 1,4-cyclohexadiene and propene) are easily separable and of commercial value, especially as they are bio-derived. The E Factor for the production of 2-vinylphenol by our process is also very low compared with those of previously reported syntheses. © 2019 The Royal Society of Chemistry.
- ItemThe effect of supported MoOX structures on the reaction pathways of propene formation in the metathesis of ethylene and 2-butene(Cambridge : RSC, 2014) Hahn, T.; Kondratenko, E.V.; Linke, D.The kind of surface MoOX structures on Al2O3–SiO2 was found to determine propene selectivity in the metathesis of ethylene and 2-butene. Compared to isolated tetrahedral MoOX species, their polymerized octahedral counterparts show significantly lower activity for isomerisation of 2- to 1-butene thus hindering non-selective metathesis of these butenes. In addition, they reveal higher ability to engage ethylene in propene formation.
- ItemCorrection: A robust iron catalyst for the selective hydrogenation of substituted (iso)quinolones(Cambridge : RSC, 2018) Sahoo, Basudev; Kreyenschulte, Carsten; Agostini, Giovanni; Lund, Henrik; Bachmann, Stephan; Scalone, Michelangelo; Junge, Kathrin; Beller, MatthiasThe authors regret that the term “(iso)quinolones” was used throughout the article, including the title, when the correct term should be “(iso)quinolines”. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.
- ItemUnprecedented selective homogeneous cobalt-catalysed reductive alkoxylation of cyclic imides under mild conditions(Cambridge : RSC, 2017) Cabrero-Antonino, Jose R.; Adam, Rosa; Papa, Veronica; Holsten, Mattes; Junge, Kathrin; Beller, MatthiasThe first general and efficient non-noble metal-catalysed reductive C2-alkoxylation of cyclic imides (phthalimides and succinimides) is presented. Crucial for the success is the use of [Co(BF4)2·6H2O/triphos (L1)] combination and no external additives are required. Using the optimal cobalt-system, the hydrogenation of the aromatic ring of the parent phthalimide is avoided and only one of the carbonyl groups is selectively functionalized. The resulting products, N- and aryl-ring substituted 3-alkoxy-2,3-dihydro-1H-isoindolin-1-one and N-substituted 3-alkoxy-pyrrolidin-2-one derivatives, are prepared under mild conditions in good to excellent isolated yields. Intramolecular reductive couplings can also be performed affording tricyclic compounds in a one-step process. The present protocol opens the way to the development of new base-metal processes for the straightforward synthesis of functionalized N-heterocyclic compounds of pharmaceutical and biological interest.
- ItemEfficient and selective hydrogenation of amides to alcohols and amines using a well-defined manganese-PNN pincer complex(Cambridge : RSC, 2017) Papa, Veronica; Cabrero-Antonino, Jose R.; Alberico, Elisabetta; Spanneberg, Anke; Junge, Kathrin; Junge, Henrik; Beller, MatthiasNovel well-defined NNP and PNP manganese pincer complexes have been synthetized and fully characterized. The catalyst Mn-2 containing an imidazolyaminolphosphino ligand shows high activity and selectivity in the hydrogenation of a wide range of secondary and tertiary amides to the corresponding alcohols and amines, under relatively mild conditions. For the first time, more challenging substrates like primary aromatic amides including an actual herbicide can also be hydrogenated using this earth-abundant metal-based pincer catalyst.
- ItemCobalt-catalysed reductive C-H alkylation of indoles using carboxylic acids and molecular hydrogen(Cambridge : RSC, 2017) Cabrero-Antonino, Jose R.; Adam, Rosa; Junge, Kathrin; Beller, MatthiasThe direct CH-alkylation of indoles using carboxylic acids is presented for the first time. The catalytic system based on the combination of Co(acac)3 and 1,1,1-tris(diphenylphosphinomethyl)-ethane (Triphos, L1), in the presence of Al(OTf)3 as co-catalyst, is able to perform the reductive alkylation of 2-methyl-1H-indole with a wide range of carboxylic acids. The utility of the protocol was further demonstrated through the C3 alkylation of several substituted indole derivatives using acetic, phenylacetic or diphenylacetic acids. In addition, a careful selection of the reaction conditions allowed to perform the selective C3 alkenylation of some indole derivatives. Moreover, the alkenylation of C2 position of 3-methyl-1H-indole was also possible. Control experiments indicate that the aldehyde, in situ formed from the carboxylic acid hydrogenation, plays a central role in the overall process. This new protocol enables the direct functionalization of indoles with readily available and stable carboxylic acids using a non-precious metal based catalyst and hydrogen as reductant.
- ItemBio-based building blocks from 5-hydroxymethylfurfural via 1-hydroxyhexane-2,5-dione as intermediate(Cambridge : RSC, 2019) Wozniak, Bartosz; Tin, Sergey; de Vries, Johannes G.The limits to the supply of fossil resources and their ever increasing use forces us to think about future scenarios for fuels and chemicals. The platform chemical 5-hydroxymethyl-furfural (HMF) can be obtained from biomass in good yield and has the potential to be converted in just a few steps into a multitude of interesting products. Over the last 20 years, the conversion of HMF to 1-hydroxyhexane-2,5-dione (HHD) has been studied by several groups. It is possible to convert HMF into HHD by hydrogenation/hydrolytic ring opening reaction in aqueous phase using various heterogeneous and homogeneous catalysts. This review addresses both the state of the art of HHD synthesis, including mechanistic aspects of its formation, as well as the recent progress in the application of HHD as a building block for many useful chemicals including pyrroles, cyclopentanone derivatives and triols. © 2019 The Royal Society of Chemistry.
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