Cooperative Dehydrogenation of N‐Heterocycles Using a Carbon Nanotube–Rhodium Nanohybrid

Rhodium nanoparticles were anchored on carbon nanotubes and the resulting nanohybrid was studied as co‐catalyst, along with tert‐butylcatechol, for the dehydrogenation of various N‐heterocycles. The co‐catalytic system operates in high yields, under the mildest conditions reported so far, and can be applied to a wide variety of secondary amine‐containing scaffolds.     

ALKYLIERUNGS,UND ARYLIERUNGSREAKTIONEN MIT GEMINALEN DITHIOLATEN

Abstract

Acylacetonitrile 1 reagieren mit Schwefelkohlenstoff in Gegenwart von Natriumhydrid zu den Dinatriumsalzen 2. Behandlung von 2 mit einem Alkylierungsreagens ergibt die offenkettigen oder cyclischen Acyl-cyanketen-S,S-acetale 3, 4, 8 bzw. 10. Arylierung zu 11 gelingt mit 2,4-Dinitrochlorbenzen. Fügt man zu² nur ein Äquivalent Methyliodid hinzu und säuert das Reaktionsgemisch an, so entstehen die monoalkylierten Verbindungen 7, während β-Hydroxythioanilide 12 durch Umsetzung von 1 mit Phenylisothiocyanat zugänglich sind. Ein Vergleich der δ-Werte zeigt, daß in 7 und 12 der gleiche Typ für die Chelatisierung des Protons der OH-Gruppe vorliegt.

Acyl acetonitriles 1 react with carbon disulfide in the presence of sodium hydride to give disodium salts 2. Treatment of 2 with an alkylation reagent yields the open chain or cyclic acyl cyanketene S,S-acetals 3,4,8 and 10, respectively. Arylation to 11 is successful with 2,4-dinitro-chlorobenzene. Adding only one equivalent of methyl iodide to 2 and acidifying the reaction mixture lead to the monoalkylated compounds 7, whereas β-hydroxythioanilides 12 are available by reaction of 1 with phenyl isothiocyanate. A comparison of the δ-values shows that there exists the same type of the proton's chelation of the OH-group in 7 and 12.     

Liquid Formulations for Long-Term Storage of Monoclonal IgGs

Proteins like immunoglobulin (IgGs) are prone to degradation by a variety of pathways. In this study, a stabilizing formulation for long-term storage of a panel of seven monoclonal IgGs was found using differential scanning calorimetry (DSC). In the chosen formulations, the IgGs were subjected to stress, accelerated and real-time storage, and analyzed by size exclusion chromatography to determine fragment and aggregate content, and fluorescence-activated cell sorting to measure immunoreactivity. All IgGs showed the greatest conformational stability near their isoelectric point which was enhanced by adding sorbitol, sucrose, glycine, and sodium chloride. Optimized formulations, found by DSC, containing 20 % sorbitol and 1 M glycine prevented IgG aggregation and fragmentation and conserved immunoreactivity against shear stress, multiple freeze–thaw cycles, accelerated storage at 37 °C, and 12 months storage at 4 and ?20 °C. Relatively poor thermal stability of the antigen-binding fragment domain was shown to limit storage stability of IgGs. This study confirms the predictive power of DSC to find storage formulations which protect IgGs during stress and long-term storage from aggregation and degradation. Liquid formulations found in this study may have a broad utility for other IgGs.     

Wet-Chemically Prepared Porphyrin Layers on Rutile TiO2(110)

Porphyrins are large organic molecules that are interesting for different applications, such as photovoltaic cells, gas sensors, or in catalysis. For many of these applications, the interactions between adsorbed molecules and surfaces play a crucial role. Studies of porphyrins on surfaces typically fall into one of two groups: (1) evaporation onto well-defined single-crystal surfaces under well-controlled ultrahigh vacuum conditions or (2) more application-oriented wet chemical deposition onto less well-defined high surface area surfaces under ambient conditions. In this study, we will investigate the wet chemical deposition of 5-(monocarboxyphenyl)-10,15,20-triphenylporphyrin (MCTPP) on well-defined rutile TiO₂(110) single crystals under ambient conditions. Prior to deposition, the TiO₂(110) crystals were also cleaned wet-chemically under ambient conditions, meaning none of the preparation steps were done in ultrahigh vacuum. However, after each preparation step, the surfaces were characterized in ultrahigh vacuum with X-ray photoelectron spectroscopy (XPS) and the result was compared with porphyrin layers prepared in ultrahigh vacuum (UHV) by evaporation. The differences of both preparations when exposed to zinc ion solutions will also be discussed.     

Nanoparticle directed domain orientation in thin films of asymmetric block copolymers

We investigated the thin film morphology of two different asymmetric block copolymers (BCP), polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) and poly(n-pentyl methacrylate)-block-poly(methyl methacrylate) (PPMA-b-PMMA), loaded with pre-synthesized iron oxide nanoparticles (NP). The chemical composition of the BCP constituents determines the strength of the interaction between polymer chains and nanoparticles. In the case of NP/PS-b-P4VP system, the nanoparticles interact preferentially with the P4VP block and hence localize selectively in the P4VP cylindrical microdomains. However, for the NP/PPMA-b-PMMA system, the nanoparticles have no significant preference for the copolymer blocks and segregate at the polymer/substrate interface. Interestingly, this changes the effective substrate surface energy and hence leads to a remarkable change in domain orientation from parallel to perpendicular with respect to the substrate. These results clearly demonstrate the importance of both enthalpic and entropic factors which determine spatial distribution of NP in BCP films and influence domain orientation.     

Tapered copolymers of styrene and 4-vinylbenzocyclobutene via carbanionic polymerization for crosslinkable polymer films

Well-defined polystyrene homopolymers with surface-adhesive triethoxysilyl end group were synthesized via living carbanionic polymerization, epoxide end-functionalization and subsequent hydrosilylation with triethoxysilane. Grafting-to performance of polymers with various molecular weight (M_n = 3000–14,000 g mol⁻¹) to a silicon surface was examined in dependence of reaction time, polymer concentration, solvent and number of alkoxysilyl end groups. Crosslinkable polymers for surface modification were synthesized by statistical carbanionic copolymerization of 4-vinylbenzocyclobutene (4-VBCB) and styrene, followed by epoxide end-functionalization and triethoxysilane modification (M_n = 4000–14,000 g mol⁻¹). The copolymers were characterized by ¹H-NMR, THF-SEC, and matrix-assisted laser desorption and ionization time-of-flight mass spectrometry. In situ ¹H-NMR kinetic studies in cyclohexane-d₁₂ provided information regarding the monomer gradient in the polymer chains, with styrene being the more reactive monomer (r_s = 2.75, r_4-VBCB = 0.23). Thin polymer films on silicon wafers were prepared by grafting-to surface modification under conditions derived for the polystyrene homopolymer. The traceless, thermally induced crosslinking reaction of the benzocyclobutene units was studied by DSC in bulk as well as in 3–6 nm thick polymer films. Crosslinked films were analyzed by atomic force microscopy, ellipsometry, and nanoindentation, showing smooth polymer films with an increased modulus. © 2019 The Authors. Journal of Polymer Science published by Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 181–192     

Deoxygenation of Epoxides with Carbon Monoxide

The use of carbon monoxide as a direct reducing agent for the deoxygenation of terminal and internal epoxides to the respective olefins is presented. This reaction is homogeneously catalyzed by a carbonyl pincer-iridium(I) complex in combination with a Lewis acid co-catalyst to achieve a pre-activation of the epoxide substrate, as well as the elimination of CO₂ from a γ-2-iridabutyrolactone intermediate. Especially terminal alkyl epoxides react smoothly and without significant isomerization to the internal olefins under CO atmosphere in benzene or toluene at 80–120 °C. Detailed investigations reveal a substrate-dependent change in the mechanism for the epoxide C−O bond activation between an oxidative addition under retention of the configuration and an S_N2 reaction that leads to an inversion of the configuration.