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Lejkowski M.,RWTH Aachen | Lejkowski M.,Hte Aktiengesellschaft | Banerjee P.,RWTH Aachen | Banerjee P.,Indian Institute of Technology Ropar | And 2 more authors.
European Journal of Organic Chemistry | Year: 2014

A modular enantioselective synthesis of spiroketals, spiroethers, and oxabicycles, each containing a dihydropyran subunit, is described. It is based on the 2,2-spiro- and 2,6-bicycloannulation of sulfoximine-substituted 2-hydroxy-dihydropyrans. Key steps of the spiroannulations are the ring-closing metathesis of the corresponding 2,2-oxadienyl and 2,6-dienyl dihydropyrans and Prins cyclization of 2-alkenyl 2-hydroxy-dihydropyrans. Ring-closing metathesis of the corresponding 2,6-dienyl dihydropyrans gave oxabicycles with oxabicyclo[4.3.1]decane skeletons. These routes were extended to the synthesis of spiroketals and spiroethers incorporating additional annulated six-membered rings. Diastereoselective Prins cyclization of mono- and bicyclic 2-alkenyl-2-hydroxy-dihydropyrans was highly selective and afforded chloro-substituted spirocycles. Substituted 2-hydroxy-dihydropyrans were obtained through cyclization of δ-hydroxy ketones, which were synthesized from enantiomerically pure sulfoximine-substituted homoallylic alcohols through lithiation and trapping of the α-lithioalkenylsulfoximines with unsaturated aldehydes, followed by allylic oxidation. Inter- and intramolecular glycosidations of the 2-hydroxy-dihydropyrans with O- and C-nucleophiles proceeded with high stereoselectivities and furnished 2,6-trans-configured glycosides. Dihydropyran oxocarbenium ions are most likely intermediates in the glycosidations. According to ab initio calculations, sulfoximine- and trimethyl-substituted dihydropyran oxocarbenium ions adopt a half-chair-like conformation. The energy difference between the oxocarbenium ion with pseudoaxial and the one with pseudoequatorial methyl groups is very small. A transition state model for their reactions with nucleophiles is proposed. It features a half-chair-like conformation, a pseudoequatorial C6 substituent, and an anti-addition of the nucleophile along an axial trajectory to C2 that produces an anti-periplanar lone pair at the O atom. A similar transition state model allows a general explanation for the trans stereoselectivity of the reactions between C6-substituted dihydropyran oxocarbenium ions and nucleophiles. Spiroannulation of 2-hydroxy-dihydropyrans through RCDEM of the corresponding 2,2-dienyl dihydropyrans and Prins cyclization of 2-alkenyl dihydropyrans gave sulfoximine-substituted unsaturated spiroketals and spiroethers. RCDEM of 2,6-dienyl dihydropyrans afforded oxabicycles. A transition state model for the 2,6-trans-stereoselective glycosidation of dihydropyran oxocarbenium ions is proposed. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Forster T.,TU Munich | Schunk S.A.,Hte Aktiengesellschaft | Jentys A.,TU Munich | Lercher J.A.,Hte Aktiengesellschaft
Chemical Communications | Year: 2011

Co and Mn polysiloxanes are unique catalyst/initiator systems for the liquid phase oxidation of o-xylene showing higher activity than Co naphthenates, which is related to the weak interaction of the polar products with the hydrophobic surface as well as the absence of hydroxyl groups and surrounding oxygenates limiting radical quenching. © 2011 The Royal Society of Chemistry.


Brem N.,Hte Aktiengesellschaft | Lutz F.,Hte Aktiengesellschaft | Sundermann A.,Hte Aktiengesellschaft | Schunk S.A.,Hte Aktiengesellschaft
Topics in Catalysis | Year: 2010

The use of rhodium iodide catalysts in the carbonylation reaction of glycerine leads to saturated and unsaturated acids with C4-carbon backbone which can be integrated or are products of the petrochemical value chain. The ratio of the different saturated and unsaturated products can be controlled via the reaction conditions and the catalyst to promoter ratio. A study on potential reaction pathways was included in the study; all experiments were carried out in high throughput mode. © 2009 Springer Science+Business Media, LLC.


Bohmer N.,Hte Aktiengesellschaft | Roussiere T.,Hte Aktiengesellschaft | Kuba M.,Hte Aktiengesellschaft | Schunk S.A.,Hte Aktiengesellschaft
Combinatorial Chemistry and High Throughput Screening | Year: 2012

Renewable feedstocks have been in the spotlight of intensive research activities over the past 10 years. Glycerol is one of the feedstock molecules which has been the target of numerous research efforts, for a number of reasons. First of all glycerol is currently readily available due to the fact that it is a couple product of the first generation biodiesel production. Secondly glycerol can be taken as a representative model substrate to explore the options of selective conversion of sugar alcohols to products of value. In our paper we discuss potential routes for the valorisation of glycerol which lead to intermediates already established within the petrochemical value chain and illustrate what impact high throughput experimentation may have as a success factor on research and development for this field. As illustrative examples we have chosen the oxidative transformation of glycerol to acrolein and acrylic acid and the carbonylation of glycerol to C4-acids. © 2012 Bentham Science Publishers.


Futter C.,Hte Aktiengesellschaft | Prasetyo E.,Hte Aktiengesellschaft | Schunk S.A.,Hte Aktiengesellschaft
Chemie-Ingenieur-Technik | Year: 2013

Numerous homogeneous catalyst-initiator systems are known and utilized in industrial scale to conduct various autoxidation processes. The reaction mechanism and kinetic details of homogeneous liquid phase autoxidation have been extensively investigated. This article presents an overview on the state of the art of heterogeneous catalyst-initiator systems in the liquid phase oxidation of hydrocarbons. Mechanistic insights and limitations of the heterogeneous catalyst-initiator systems are discussed. The potentials and challenges towards an industrial application are evaluated. © 2013 Wiley-VCH Verlag GmbH & Co. KGaA.


The present invention relates to an integrated system for the treatment of exhaust gases, which preferably consists of at least one NO_(x)-storing component, at least one in situ ammonia-generating component, at least one ammonia-storing component and at least one ammonia (NH_(3))-SCR-component, as well as to a process for the treatment of exhaust gas comprising at least the steps (i) storing of NO_(x) under lean exhaust gas conditions in at least one NO_(x)-storing component; (ii) in situ conversion of the stored NO_(x) to ammonia (NH_(3)) under rich exhaust gas conditions; (iii) storing of the ammonia (NH_(3)) in at least one NH_(3)-storing component under rich exhaust gas conditions as well as the (iv) reaction of NH_(3) with NO_(x) under lean exhaust gas conditions. Thereby, the partial steps storing of NO_(x) and conversion of NH_(3) with NO_(x) are carried out at least partially and/or temporarily simultaneously and/or parallelly. Furthermore, preferred catalysts are disclosed for carrying out the process.


The present invention relates to a catalysis apparatus for testing catalysts with variable process pressure adjustment over a pressure range from 0.01 millibar to 300 bar. The apparatus preferably has a plurality of reaction chambers (101, 102, . . . ) arranged in parallel, the reaction chamber outlet-side lines (211, 212, . . . ) of which are divided into two groups of sub-lines. One group of main lines (411, 412, . . . ) is operatively connected to a regulating valve (61), which is common to all of the main lines, and to an exhaust-air line (62), and the second group of secondary lines (311, 312, 313, . . . ) and switching valves (321, 322, . . . ) is operatively connected to an analysis unit (34). It is preferable for reaction chamber outlet-side lines (201, 202, . . . ) to be equipped in each case with a separate line for regulating fluid supply (211, 212, . . . ). In a preferred embodiment, the connecting points of the reaction chamber outlet-side lines (201, 202, . . . ) to the respective main lines (411, 412, . . . ) and secondary lines (311, 312, . . . ) have in each case one mixing vessel (301, 302, . . . ).


Patent
Hte Aktiengesellschaft | Date: 2010-09-28

The present invention relates to a method and a device for the parallel study of chemical reactions in at least two spatially separated reaction spaces. In particular, the invention is suitable for reactions which are not constant volume reactions and/or for reactions in which fluid flows through at least two spatially separated reaction spaces are intended to be controlled together for all the reaction spaces, or for related subsets of them, in the most straightforward way possible. According to one embodiment, the device according to the invention for the parallel study of chemical reactions comprises at least the following components: (a) at least two spatially separated reaction spaces; (b) on the reaction space input side, at least one common educt feed for the reaction spaces according to (a); (d) on the reaction space output side, at least one connection per reaction space to at least one holding gas feed common to all the reaction spaces, or subsets of them; (e) on the reaction space output side, and downstream of the connection to the holding gas feed according to (d) in the product flow direction, at least one restrictor per reaction space.


Patent
Hte Aktiengesellschaft | Date: 2011-01-12

The present invention relates to a method and a device for the parallel study of chemical reactions in at least two spatially separated reaction spaces. In particular, the invention is suitable for reactions which are not constant volume reactions and/or for reactions in which fluid flows through at least two spatially separated reaction spaces are intended to be controlled together for all the reaction spaces, or for related subsets of them, in the most straightforward way possible. According to one embodiment, the device according to the invention for the parallel study of chemical reactions comprises at least the following components: (a) at least two spatially separated reaction spaces; (b) on the reaction space input side, at least one common educt feed for the reaction spaces according to (a); (d) on the reaction space output side, at least one connection per reaction space to at least one holding gas feed common to all the reaction spaces, or subsets of them; (e) on the reaction space output side, and downstream of the connection to the holding gas feed according to (d) in the product flow direction, at least one restrictor per reaction space.


Patent
Hte Aktiengesellschaft | Date: 2012-07-30

The present invention relates to a process for handling product fluid streams which are obtained in the catalytic hydrogenation of liquid feeds in laboratory catalysis apparatuses. The liquid feeds are preferably hydrocarbons comprising sulfur- and nitrogen-comprising compounds as impurities. The hydrogenation serves to convert the impurities into hydrogen sulfide and ammonia which in this form can be readily separated off from the other constituents of the liquid feed. The product fluid streams are contacted with an inert gas stream, with the flow rate of the inert gas being a multiple of the flow rate of the product fluid stream. The formation of deposits in lines of the region on the outlet side of the reaction space can be effectively prevented by means of the process of the invention.

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