Catalytic Asymmetric Aminohydroxylation with Amino-Substituted Heterocycles as Nitrogen Sources

The suprafacial, vicinal addition of a heterocyclic moiety and a hydroxyl group is achieved by the osmium-catalyzed asymmetric aminohydroxylation (AA) of olefins with amino-substituted heterocycles as the nitrogen sources. Amino alcohols are obtained in up to 97 % yield and with up to 99 % ee when a ligand derived from dihydroquinidine (DHQD-L) is used [Eq. (1); Rⁱ indicates the remaining portion of the heterocycle (Het); H₂O is the O source]. The AA can now be considered as a means to directly introduce complex, biologically relevant substructures to hydrocarbon backbones.     

Carbon−Fluorine Bond Formation via a Five-Coordinate Fluoro Complex of Ruthenium(II), Preliminary Communication

The 16-electron, five-coordinate fluoro complex [RuF(dppp)₂]PF₆ ( 1a ; dppp=propane-1,3-diylbis[diphenylphosphine] smoothly reacts with 1,3-diphenylallyl bromide (=1,1′-(3-bromoprop-1-ene-1,3-diyl)bis[benzene]) in dry CDCl₃ to give 1,3-diphenylallyl fluoride and [RuBr(dppp)₂]⁺ in nearly quantitative yield. Under similar conditions, bromide (or chloride)/fluoride exchange also occurs with chlorotriphenylmethane, bromodiphenylmethane, and tert-butyl bromide. The crystal structure of 1a is reported.     

Laser ablation of energetic polymer solutions: effect of viscosity and fluence on the splashing behavior

Laser plasma thrusters are a new kind of propulsion system for small satellites, and work with the thrust created by the laser ablation of a target. Liquid polymer solutions are very promising fuels for such systems, provided that no splashing of the target occurs, because ejection of droplets strongly decreases the performances of the system. We have investigated the nanosecond infrared laser ablation of glycidyl azide polymer solutions containing carbon nanoparticles as absorber. Shadowgraphy imaging revealed two cases, namely splashing regime and solid-like behavior. The transition between both regimes depends on the viscosity of the solution and on the laser fluence, and is explained by the recoil force acting on the target. Appropriate conditions to avoid splashing were identified, showing that this liquid polymer solution is a suitable fuel for laser plasma thrusters.     

Microfluidic HPLC‐Chip devices with integral channels containing methylstyrenic‐based monolithic media

Polyimide HPLC‐Chip devices containing poly(methylstyrene‐bis‐p‐vinylphenyl)ethane (MS/BVPE) stationary phase within the device channels and with wall attachment were prepared by thermally initiated free radical polymerization. The microfluidic devices were coupled to both UV and MS detectors. The potential of the MS/BVPE monolith as an alternative separation media within chip devices was investigated by side‐by‐side comparisons to particulate media within commercial devices. The chromatographic behavior of this stationary phase was comparable to particulate media for separations of proteins as the average peak width at half‐height was equal (6.2 s) for a separation within 8 min under gradient elution conditions. The ability to control the porosity characteristics of the MS/BVPE monolith with changes in polymerization time also extended its utility into small analyte (< 500 Da) applications, although more optimization is needed to match conventional RP media for these applications. The good mechanical stability of the MS/BVPE monolith within the microdevices enabled excellent run‐to‐run repeatability (%RSD retention time (? 0.16) and chip‐to‐chip reproducibility (%RSD retention time (1.4). The use of this material within enrichment channels also shows its potential value in more complex work flows.     

State Reconstruction in Higher Dimensional PDEs with Spatially Varying Parameters

The state estimation problem is considered for a diffusion-reaction system with spatially varying parameters defined on a 3-dimensional rectangular domain with the measured output being restricted to a single surface. For this, a backstepping-based observer design is applied, which enables to obtain the observer gains such that the observer error dynamics decays exponentially in the L₂-norm. At first, an idealized system output restricted to a single surface is assumed as an available measurement. Secondly, in view of a practical realization of the proposed observer, the idealized system output is reconstructed from a set of finite-dimensional measurements. The observer error convergence and the applicability of the proposed approach are evaluated by means of numerical simulations. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)