Amine-Catalyzed Cascade Reactions of Unprotected AldosesAn Operationally Simple Access to Defined Configured Stereotetrads or Stereopentads

An amine-catalyzed cascade reaction of unprotected carbohydrates with 1.3-diketones was elaborated. This cascade is based on a Knoevenagel reaction/intramolecular ketalization/retro-aldol reaction. By application of this operationally simple protocol, a direct access to optically active stereopentads or stereotetrads is given. Rules of configurative outcomes will be discussed

Depth-Dependent Structural Changes in PS‑<i>b</i>‑P2VP Thin Films Induced by Annealing

GISAXS measurements with scattering contrast matching at the silicon K-edge were performed to obtain depth-resolved information on structural changes in as-spun and annealed PS-<i>b</i>-P2VP thin films on silicon substrate. Depth-sensitive GISAXS measurements of the as-spun film revealed a vertically oriented fingerprint-like lamellar structure with a microphase separation distance of 59 nm throughout the entire film. The annealed film showed a significantly reduced ordering at the surface to a depth of about 30 nm, while the order is preserved toward the substrate interface. At the same time, no significant transition to horizontal ordering was observed after 2 h of annealing at 105 °C. We conclude that the transition process from vertical to horizontal ordering is incomplete after the annealing time and remains in a frozen state at room temperature. Moreover, the transition starts as a disorder increase at the top of the film, which indicates a higher mobility of the coalescing microdomains at the surface

Design of a Nanometric AlTi Additive for MgB₂‑Based Reactive Hydride Composites with Superior Kinetic Properties

Solid-state hydride compounds are a promising option for efficient and safe hydrogen-storage systems. Lithium reactive hydride composite system 2LiBH₄ + MgH₂/2LiH + MgB₂ (Li-RHC) has been widely investigated owing to its high theoretical hydrogen-storage capacity and low calculated reaction enthalpy (11.5 wt % H₂ and 45.9 kJ/mol H₂). In this paper, a thorough investigation into the effect of the formation of nano-TiAl alloys on the hydrogen-storage properties of Li-RHC is presented. The additive 3TiCl₃·AlCl₃ is used as the nanoparticle precursor. For the investigated temperatures and hydrogen pressures, the addition of ∼5 wt % 3TiCl₃·AlCl₃ leads to hydrogenation/dehydrogenation times of only 30 min and a reversible hydrogen-storage capacity of 9.5 wt %. The material containing 3TiCl₃·AlCl₃ possesses superior hydrogen-storage properties in terms of rates and a stable hydrogen capacity during several hydrogenation/dehydrogenation cycles. These enhancements are attributed to an in situ nanostructure and a hexagonal AlTi₃ phase observed by high-resolution transmission electron microscopy. This phase acts in a 2-fold manner, first promoting the nucleation of MgB₂ upon dehydrogenation and second suppressing the formation of Li₂B₁₂H₁₂ upon hydrogenation/dehydrogenation cycling