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Ubliche Entwicklungsbestrebungen haben zum Ziel, Schwingungsphanomene in Antriebsstrangen von Kraftfahrzeugen zu reduzieren, etwa durch aktive Schwingungstilgung. Im Gegensatz hierzu steht die kontrollierte Anregung von Eigenschwingungen bei dem in diesem Beitrag vorgestellten ,,Resonanzstart-Verfahren“ fur Verbrennungsmotoren. Durch die hiermit erreichte Absenkung des erforderlichen Elektromaschinen-Drehmoments werden beispielsweise Mild-Hybride ohne konventionellen Anlasser ermoglicht. Die fur eine passive Schwingungsisolation vorteilhafte, drehweiche Verbindung von Elektromaschinen-Rotor und Kurbelwelle ist hierbei Herausforderung und Nutzbringer zugleich.

The synthesis and characterization of oligomeric poly(acetalcarbonates) obtained with the use of formaldehyde as a sustainable and renewable C1-building block is reported. Our approach involves generating monomeric formaldehyde in situ by depolymerisation of paraformaldehyde and repolymerisation to oligomeric poly(acetalcarbonates) using a bifunctional catalyst combination comprising a Lewis acid and Cs2CO3. Analysis of the chemical structure of the products revealed the presence of oligomeric polyoxymethylene sequences together with carbonate units and oxyethylene units along the polymer chain. The latter units act as zip stoppers, and lead to significant stabilisation of the polymer chains. Terminal OH groups allow for rich follow-up chemistry and render as products interesting bifunctional polymer building blocks.

Polyketones with low CO content and molecular weight in the oligomer range were obtained with unprecedented efficiency by using a new protocol for the palladium-catalysed copolymerisation of CO and ethylene. Key physicochemical properties such as resistance to degradation and melting point were traced back to the microstructure of the polyketones. With properties tailored to the application, non-alternating polyketones emerge as interesting materials for demanding applications, where alternating polyketones are currently being used. Furthermore, the keto groups constitute interesting anchoring sites for introducing functionalities.

An efficient access to configurationally stable α,α-disubstituted α-amino aldehydes, oxazolidinones, and α-amino acids has been presented. Starting from simple and easily available racemic aldehydes, the α-aminated products were obtained using azodicarboxylates as the nitrogen source in up to 86 % ee and moderate to excellent yield. These products could further be converted both into the corresponding α-amino alcohols and, depending on the residue of the azodicarboxylates and the reaction conditions, into the oxazolidinones. On the other hand, oxidation towards the carboxylic acid and cleavage of the hydrazide bond under mild conditions revealed the free α-alkylated phenylglycine derivative. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Proline-catalysed reactions between α-branched aldehydes and sulfonyl azides provide scalemic configurationally stabilised α-sulfamidated products with ee values of up to 86 %. The reactions can also be carried out in a one-pot fashion, with catalyst, aldehyde, sulfonyl chloride and sodium azide. The proposed mechanism differs fundamentally from the mechanistic model usually ascribed to enamine catalysis, containing as a key step the diastereoselective cycloaddition of the azide to an enamine formed in situ. The products obtained in the reaction can be converted into the corresponding unnatural amino acids in two additional steps.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

We have formulated a model for the coupled dynamics of the local polarization and the elastic deformations of dipolar glasses. Randomly interacting dipoles undergo a phase transition to a glassy state, which is signalled above Tc by a divergence of the relaxation time of the dipolar autocorrelation. Dipolar dynamics is directly observable in the dynamic dielectric susceptibility, for which we predict a power law dependence on frequency at and close to Tc. The slowing down of dipolar degrees of freedom also gives rise to dynamic critical anomalies in the elastic and structural properties, like the appearance of a central peak and divergence of the sound damping. All these phenomena are a consequence of dynamic scaling of the dipolar autocorrelation and hence interrelated. We discuss two scaling functions in detail: One is calculated within mean field theory and the other one is taken from numerical simulations of short range Ising spin glasses. The predictions of the model are in accordance with most experimental findings for dipolar glasses.

The activation of CO2 is highlighted for two lead-structures of cobalt- and zinc-based homogeneous catalysts used in the copolymerization of epoxides and CO2. Following the activation of CO2 with in situ ATR-IR spectroscopy, a surprisingly facile insertion of CO2 into metal–phenoxide bonds was revealed. Electronic supplementary information (ESI) available: Experimental details, full NMR spectrum of 1, analysis of coordination geometry, additional in situ IR spectra. See DOI: 10.1039/c3gc40147b This article is part of themed collection: Green Solvents Refereed/Peer-reviewed

An environmentally friendly method for synthesis of amides is presented where a simple ruthenium catalyst mediates the direct coupling between an alcohol and an amine with the liberation of two molecules of dihydrogen. The active catalyst is generated in situ from an easily available ruthenium complex, an N-heterocyclic carbene and a phosphine. The reaction allows primary alcohols to be coupled with primary alkylamines to afford the corresponding secondary amides in good yields. The amide formation presumably proceeds through a catalytic cycle where the intermediate aldehyde and hemiaminal are both coordinated to the metal catalyst.

Chiral amines play a pivotal role in fine chemical and natural product syntheses and the design of novel materials.

The class of α,α-disubstituted α-amino acids has gained considerable attention in the past decades and continues doing so. The ongoing interest in biological and chemical properties of the substance class has inspired the development of many new methodologies for their asymmetric construction, which have not found their way into the general focus of organic chemistry yet. The aim of this review is to provide an overview of the developments in the field since 1998.

The class of alpha,alpha-disubstituted alpha-amino acids has gained considerable attention in the past decades and continues doing so. The ongoing interest in biological and chemical properties of the substance class has inspired the development of many new methodologies for their asymmetric construction, which have not found their way into the general focus of organic chemistry yet. The aim of this review is to provide an overview of the developments in the field since 1998.

Proline-catalysed amination of alpha,alpha-disubstituted racemic aldehydes with azodicarboxylates proceeds smoothly to give configurationally stable scalemic aldehydes and oxazolidinones in up to 86% ee.

The amidation of a benzoic acid derivative attached to solid support via the T1 triazene linkage has been described. In the presence of a tin amide reagent, smooth amidations take place with primary and secondary amines to give benzamides. Anilines failed under the reaction condition employed. The progress and the success of the reaction were monitored by 1 H NMR spectroscopy using a novel direct

During the hydrogenation of oximes, the temporary protection of the nitrogen moiety by a hydroxyl group promises to provide access to a highly selective synthetic route to primary amines. We will show that the reaction, however, proceeds via the more general network of imine and Schiff base chemistry. By choosing the right catalyst and conditions, specific pathways can be selected enabling us to steer the route from a pool of intermediate compounds to either primary or secondary amines. Thus, nickel catalysts provide high selectivity towards primary amines albeit at a moderate activity, while noble metal catalysts show good selectivity towards secondary amines, as well as high activity. Detailed analysis of the reaction sequence over Ni/SiO2 provides insight into the pathways and provides understanding for the tools to obtain outstanding selectivities in the hydrogenation of oximes and other amine precursors.

Irradiation par des impulsions laser Nd-YAG de 10 ns de demi-largeur d'echantillons de polydimethylsiloxane et polystyrene; analyse des spectres de masse obtenus en mode ion positif