Complex Surface Chemistry of an Otherwise Inert Solvent Molecule: Tetrahydrofuran on Si(001)

The reaction of tetrahydrofuran (THF), an otherwise inert solvent molecule, on Si(001) was experimentally studied in ultra‐high vacuum. Using scanning tunneling microscopy (STM) and photoelectron spectroscopy at variable temperature, we could both isolate a datively bound intermediate state of THF on Si(001), as well as the final configuration that bridges two dimer rows of the Si(001) surface after ether cleavage. The latter configuration implies splitting of the O?C bond, which is typically kinetically suppressed. THF thus exhibits a hitherto unknown reactivity on Si(001).     

The dependence of the mass identification scale on different track formation models

From the very beginning of solid state track detector measurements two track formation theories were used: the models of the restricted energy loss (RED and the primary ionization (PI). Both theories include different adjustable parameters. Performing the calibration at the same ion (e.g. Fe) the differences of the mass determination as a function of charge for both track formation theories will be shown. The calculations will be compared with experimental data.     

Synthesis, cytotoxicity and cellular uptake studies of N3 functionalized Re(CO)3 thymidine complexes

Nucleoside-derived drugs play an important role in the treatment of cancer. Here, we present the synthesis and characterization of an intriguing series of N3 conjugated Re(CO)(3) thymidine complexes. The complexes were characterized by NMR spectroscopy and mass spectrometry and their cytotoxicity was assessed against A549 cells. A similar dependence on the spacer length and the toxicity has been found for N3 functionalized complexes as recently reported for their C5' counterparts. A remarkable cytotoxic complex 22, carrying a dodecylene spacer at position N3 with a bis-quinoline metal chelate moiety, with an IC(50) value of 3.4 ± 1.6 μM, has been identified. Addition of a 100-fold excess of thymidine did not statistically reduce the observed cytotoxicity of all complexes. Cellular uptake studies of complex 22 have been performed by fluorescent microscopy, showing that compound 22 was clearly internalized into A549 cells. Temperature dependent uptake studies, blocking experiments with thymidine, and endosomal co-localization suggest that uptake of 22 occurs via passive diffusion and endocytosis.     

Continuous Heterogeneous Photocatalysis in Serial Micro‐Batch Reactors

Solid reagents, leaching catalysts, and heterogeneous photocatalysts are commonly employed in batch processes but are ill‐suited for continuous‐flow chemistry. Heterogeneous catalysts for thermal reactions are typically used in packed‐bed reactors, which cannot be penetrated by light and thus are not suitable for photocatalytic reactions involving solids. We demonstrate that serial micro‐batch reactors (SMBRs) allow for the continuous utilization of solid materials together with liquids and gases in flow. This technology was utilized to develop selective and efficient fluorination reactions using a modified graphitic carbon nitride heterogeneous catalyst instead of costly homogeneous metal polypyridyl complexes. The merger of this inexpensive, recyclable catalyst and the SMBR approach enables sustainable and scalable photocatalysis.     

Total Synthesis of the Postulated Structure of Fulicineroside

A total synthesis of the proposed structures of fulicineroside and its aglycone fulicinerine is reported. The tetrasubstituted dibenzofuran substructure was accessible either through a Pd‐mediated ortho‐metalation or by an Ir‐catalyzed meta‐borylation. The synthesis of the β,β,α‐linked trisaccharide consisting of D ‐olivose, L ‐rhodinose, and L ‐rhamnose was challenged by the unprecedented β‐linked rhodinose. A Pd‐catalyzed β‐selective glycosylation of a 4‐epi‐rhodinose and a subsequent Mitsunobu inversion provided selectively the β‐linked L ‐rhodinose‐L ‐rhamnose disaccharide. Comparison with the reported data for the natural product and the aglycone suggests a misassignment of the structure of the natural product.     

Chemische Zusammensetzung der kosmischen Strahlung niederenergetischer Teilchen vonZ=12 bisZ=28, gemessen in Plastikdetektoren

Results of a balloon flight experiment flown from Fort Churchill, Canada, at 1.8 g/cm² for about 10 hours in 1968 are presented. The study was made using Lexan polycarbonate plastic sheets as a particle detector. The analysis of the flux and the charge composition is based on the measurement of 313 stopping particles from Mg to Ni with energies between 150 and 400 MeV/Nucl. The identification of the tracks of the particles is achieved using the restricted energy loss criterion. The flux is corrected for scanning and detector efficiency corresponding to their charge. We are able to measure the charge of a particle with an accuracy of ±0.3 charge units in the region of the iron peak. This accuracy depends on the detailed study of the cone length versus residual range. The evenZ to oddZ ratio for chargesZ≧20 is 3. We have measured the ratios of Mn/Fe=0.34, Cr/Fe=0.42 and Ca+Sc+Ti/Fe=1.05. From these measured charge ratios a thickness of (3±1) g/cm² interstellar matter can be deduced.     

Synthesis of Aryl- and Alkyl-Containing 3-Methylene-5-hydroxy Esters via a Barbier Allylation Reaction

The formation of C−C bonds via the allylation of carbonyl compounds has been widely applied in total syntheses. Amongst the many possible strategies, the Barbier-type allylation in aqueous media has received only moderate attention over the last decades despite its mild reaction conditions. In this study, we investigated the indium (In⁰) and zinc (Zn⁰) mediated Barbier allylation reaction to efficiently synthesize base-labile 3-methylene-5-hydroxy containing building blocks for natural product total synthesis. As model study we selected the allylation of lipidic undecanal with ethyl 3-(bromomethyl)but-3-enoate in the presence of either Zn⁰ or In⁰ and investigated the effects of additives on yields and selectivities. We then applied the optimized reaction conditions to sterically demanding allyl bromides and functionalized aromatic aldehydes yielding eleven new homoallylic alcohols, one of which was further transformed via oxidation and reduction sequences.     

Copper-catalyzed formation of C-O bonds by direct α-C-H bond activation of ethers using stoichiometric amounts of peroxide in batch and continuous-flow formats

Peroxides and ethers in flow: 2-Carbonyl-substituted phenols and β-ketoesters react safely with ethers in a microreactor environment using a copper catalyst and an organic peroxide (TBHP). This protocol results in unsymmetrical acetal scaffolds not easily available otherwise (see scheme).     

Eine Eigenschaft primitiver Primteiler vonΦ d(a)

Ohne Zusammenfassung