Design and Performance Validation of a Conductively Heated Sealed-Vessel Reactor for Organic Synthesis.

A newly designed robust and safe laboratory scale reactor for syntheses under sealed-vessel conditions at 250 °C maximum temperature and 20 bar maximum pressure is presented. The reactor employs conductive heating of a sealed glass vessel via a stainless steel heating jacket and implements both online temperature and pressure monitoring in addition to magnetic stirring. Reactions are performed in 10 mL borosilicate vials that are sealed with a silicone cap and Teflon septum and allow syntheses to be performed on a 2-6 mL scale. This conductively heated reactor is compared to a standard single-mode sealed-vessel microwave instrument with respect to heating and cooling performance, stirring efficiency, and temperature and pressure control. Importantly, comparison of the reaction outcome for a number of different synthetic transformations performed side by side in the new device and a standard microwave reactor suggest that results obtained using microwave conditions can be readily mimicked in the operationally much simpler and smaller conventionally heated device.

Microwave-assisted parallel synthesis of fused heterocycles in a novel parallel multimode reactor.

New rotor types using disposable glass vials for small-scale parallel synthesis in multimode microwave reactors are introduced. One rotor comprises 16 groups of four vials, whereas the second uses four silicon carbide plates with a 6 x 4 matrix to process the vials. Both rotors achieve utmost temperature homogeneity upon microwave irradiation and can be used for microwave-mediated reactions at temperatures of up to 200 degrees C and pressures of 20 bar. The generation of three different heterocycle libraries furnishing thiophenes, oxindoles, and benzimidazoles using the new rotor types is described.

Evaluation of Additional Track Parameters from Fluorescent Nuclear Track Detectors to Determine the LET of Individual Ions.

The measurement of single-track intensity in fluorescence nuclear track detectors can yield relative linear energy transfer (LET)-spectra with small line-width. The absolute determination of LET is, however, currently hampered by the inter-detector variability of crystal coloration and hence detector sensitivity. We therefore investigated the LET response of three additional quantities (average width and the variation of intensity and width along single tracks) using detectors irradiated with mono-energetic ion beams with LETs from 1.5 to 150 keV/µm in alumina. All quantities showed in fact smaller inter-detector variability, but at the same time larger line-width and limited dynamic range as the average intensity along a track. The additional quantities might therefore serve as a helpful complement, but not as a replacement for the current approach.

Development of the open-source dose calculation and optimization toolkit matRad.

PURPOSE: We report on the development of the open-source cross-platform radiation treatment planning toolkit matRad and its comparison against validated treatment planning systems. The toolkit enables three-dimensional intensity-modulated radiation therapy treatment planning for photons, scanned protons and scanned carbon ions. METHODS: matRad is entirely written in Matlab and is freely available online. It re-implements well-established algorithms employing a modular and sequential software design to model the entire treatment planning workflow. It comprises core functionalities to import DICOM data, to calculate and optimize dose as well as a graphical user interface for visualization. matRad dose calculation algorithms (for carbon ions this also includes the computation of the relative biological effect) are compared against dose calculation results originating from clinically approved treatment planning systems. RESULTS: We observe three-dimensional γ-analysis pass rates ≥ 99.67% for all three radiation modalities utilizing a distance to agreement of 2 mm and a dose difference criterion of 2%. The computational efficiency of matRad is evaluated in a treatment planning study considering three different treatment scenarios for every radiation modality. For photons, we measure total run times of 145 s-1260 s for dose calculation and fluence optimization combined considering 4-72 beam orientations and 2608-13597 beamlets. For charged particles, we measure total run times of 63 s-993 s for dose calculation and fluence optimization combined considering 9963-45574 pencil beams. Using a CT and dose grid resolution of 0.3 cm3 requires a memory consumption of 1.59 GB-9.07 GB and 0.29 GB-17.94 GB for photons and charged particles, respectively. CONCLUSION: The dosimetric accuracy, computational performance and open-source character of matRad encourages a future application of matRad for both educational and research purposes.

Microwave-Assisted Syntheses in Recyclable Ionic Liquids: Photoresists Based on Renewable Resources.

The copoly(2-oxazoline) pNonOx80 -stat-pDc(=) Ox20 can be synthesized from the cationic ring-opening copolymerization of 2-nonyl-2-oxazoline NonOx and 2-dec-9'-enyl-2-oxazoline Dc(=) Ox in the ionic liquid n-hexyl methylimidazolium tetrafluoroborate under microwave irradiation in 250 g/batch quantities. The polymer precipitates upon cooling, enabling easy recovery of the polymer and the ionic liquid. Both monomers can be obtained from fatty acids from renewable resources. pNonOx80 -stat-pDc(=) Ox20 can be used as polymer in a photoresist (resolution of 1 µm) based on UV-induced thiol-ene reactions.

Rapid formation of triarylphosphines by microwave-assisted transition metal-catalyzed C-p cross-coupling reactions.

Rapid, direct transition metal-catalyzed C-P(III) cross-coupling reactions were performed by microwave dielectric heating, employing diphenylphosphine and aryl halides/triflates as substrates. Depending on the specific aryl halide/triflate precursor, the highest yields were obtained utilizing heterogeneous or homogeneous Pd or Ni catalysts in DMF or NMP in the presence of KOAc or DABCO as a base. [reaction: see text]

High-throughput microwave-assisted organic synthesis: moving from automated sequential to parallel library-generation formats in silicon carbide microtiter plates.

A 48 deep-well microtiter plate system for sealed vessel parallel microwave synthesis is described. The plate consists of a standard 6 x 8 matrix of 48 wells with a maximum working volume of 300 microL and is made out of strongly microwave-absorbing sintered silicon carbide. In combination with an alumina sealing plate equipped with adequate conical bore holes for sample withdrawal, the setup can be used for microwave processing at temperatures up to approximately 200 degrees C and 20 bar of pressure. The microtiter plate setup displays excellent temperature and reaction homogeneity and was used for the generation of a 30-member library of 2-aminopyrimidines.