In Water and under Mild Conditions: α-Alkylation of Ketones with Alcohols by Phase-Transfer-Assisted Borrowing Hydrogen Catalysis.

Borrowing hydrogen is a powerful and green technique that allows readily available alcohols to be used as alkylating agents and produces water as the only by-product. Nevertheless, harsh conditions such as high temperatures and organic solvents are usually required. Herein, we present a strategy to perform the α-alkylation of ketones in aqueous media at mild temperatures by combining borrowing hydrogen with phase-transfer catalysis. A broad scope of methyl ketones was functionalized with alkyl and benzyl alcohols in moderate to good yields at 40 °C. The protocol was also highly effective at large scale and room temperature.

Ruthenium nanoparticles ligated by cholesterol-derived NHCs and their application in the hydrogenation of arenes.

Herein we present ruthenium nanoparticles (Ru-NPs) stabilized with two rigid NHC ligands derived from cholesterol. The obtained nanoparticles were fully characterized and applied in the hydrogenation of various aromatic compounds under mild conditions. Interestingly, the more bulky ligand gives a slightly lower ligand coverage and a faster catalyst.

Addressable Cholesterol Analogs for Live Imaging of Cellular Membranes.

Cholesterol is an essential component of most biological membranes and serves important functions in controlling membrane integrity, organization, and signaling. However, probes to follow the dynamic distribution of cholesterol in live cells are scarce and so far show only limited applicability. Herein, we addressed this problem by synthesizing and characterizing a class of versatile and clickable cholesterol-based imidazolium salts. We show that these cholesterol analogs faithfully mimic the biophysical properties of natural cholesterol in phospholipid mono- and bilayers, and that they integrate into the plasma membrane of cultured and primary human cells. The membrane-incorporated cholesterol analogs can be specifically labeled by click chemistry and visualized in live-cell imaging experiments that show a distribution and behavior comparable with that of endogenous membrane cholesterol. These results indicate that the cholesterol analogs can be used to reveal the dynamic distribution of cholesterol in live cells.

Flexible design of ionic liquids for membrane interactions.

In the last years, ionic liquids gained a lot of interest in materials sciences. Especially their interactions with biomolecules like lipids or proteins became more and more fascinating. One substance class of ionic liquids are imidazolium salts, which are usually known as the precursors of the more prominent N-heterocyclic carbenes (NHCs). Due to their high stability and easy synthesis, imidazolium salts became more attractive for applications in biological systems. In 2015, imidazolium salts bearing long alkyl chains in their backbone were established as lipid analogs. Interestingly, different effects of the intercalation into a membrane can be observed depending on the characteristics of the structure. Within this tutorial, we would like to highlight the modular synthesis of these compounds leading to a versatile tool box of lipid analogs that can be adjusted depending on the required needs.

Soluble Platinum Nanoparticles Ligated by Long-Chain N-Heterocyclic Carbenes as Catalysts.

Soluble platinum nanoparticles (Pt NPs) ligated by two different long-chain N-heterocyclic carbenes (LC-IPr and LC-IMe) were synthesized and fully characterized by TEM, high-resolution TEM, wide-angle X-ray scattering (WAXS), X-ray photoelectron spectroscopy (XPS), and solution NMR. The surface chemistry of these NPs (Pt@LC-IPr and Pt@LC-IMe) was investigated by FT-IR and solid state NMR using CO as a probe molecule. A clear influence of the bulkiness of the N-substituents on the size, surface state, and catalytic activity of these Pt NPs was observed. While Pt@LC-IMe showed no activity in the hydroboration of phenylacetylene, Pt@LC-IPr revealed good selectivity for the trans-isomer, which may be supported by a homogeneous species. This is the first example of hydroboration of acetylenes catalyzed by non-supported Pt NPs.

co.labore-A Genuine Collaboration between Arts and Science, Reflecting Viewpoints and Merging Skills.

Often chemists regard their scientific work as creative, when designing and synthesizing new molecules and larger assemblies. In this, we have to go through recurring stages of planning projects, doubting results, discarding ideas, and restarting them with a different approach in order to be successful in chemical research. From this point of view, can we fairly assume that these processes are analogous to the stages artists go through when creating art? In our efforts to strengthen reflective perspectives on what chemists are doing, the SFB 858 initiated a collaboration with the Academy of Fine Arts Münster. Additionally, we were aiming to enter into a dialogue about our research with a broader public.

Modular Bidentate Hybrid NHC-Thioether Ligands for the Stabilization of Palladium Nanoparticles in Various Solvents.

The synthesis of four different bidentate hybrid NHC-thioether ligands is presented. The corresponding palladium nanoparticles are stable in various solvents, depending on the ligand used, and show high chemoselectivity in the hydrogenation of olefins. The solubility of the nanoparticles can be switched multiple times depending on the pH value of the solvent. XPS analysis (which shows a subtle shift in the binding energy) was identified as a convenient tool to establish the binding mode of NHC ligands.