Helvetica Chimica Acta最新文献

Supported catalysts are central to industrial catalytic processes. While traditional synthesis methods often yield poorly defined materials, thus complicating structural elucidation, Surface Organometallic Chemistry (SOMC) offers a solution, producing well-defined structures. Recent advances in SOMC precursor development have shown that amidinate-based complexes are a privileged class of precursors to generate supported metallic nanoparticles. In that context, this study investigates the grafting mechanism of a prototypical amidinate precursor, Ir(COD)(DIA) (1-Ir), onto SiO₂. Unique to amidinate complexes, grafting is shown to occur without ligand release, creating a reversible covalent bond. Using tris(tert-butoxy)silanol as a molecular analogue for a silanol group on SiO₂, the structure of the grafted species is elucidated by single X-Ray diffraction, comparison of IR spectroscopy, and X-Ray absorption spectroscopy (XAS) data. The reversibility of the reaction with O−H groups is demonstrated using variable-temperature NMR spectroscopy, IR spectroscopy, and is supported by DFT calculations. Notably, we show that a partial degrafting is also possible at elevated temperatures under vacuum.

Multi-resonant thermally activated delayed fluorescence (MR-TADF) helicenes show great potential as chiral emitters due to their typically high photoluminescence quantum yield and that they emit circularly polarized luminescence. Here, a new propeller-shaped chiral MR-TADF helicene DiKTa3, integrating three DiKTa moieties, was designed and synthesized aiming to achieve co-parallel electronic and magnitude transition dipole moments that would lead to a high dissymmetry factor, g. It emits at λ_PL of 491 nm, with a full width at half maximum of 52 nm and has a moderate ΔE_ST value of 0.24 eV in toluene. The separated (P,P,P) enantiomer shows an absorption dissymmetry factor |g_abs| of 6.8×10⁻⁴ at 450 nm, which results from a lower symmetry conformation adopted by the compound in solution than the C₃-symmetric optimized structure. This work highlights the strong influence that geometry can have on the chiroptical properties of the emitter.

Synthesis of a series of indolo[1,2-a]quinoxaline derivatives substituted with phthalazinones/isoindolinones/carbonyl benzoylesters at C-4 position have been accomplished under open air rt/heating conditions following ANRORC (Addition of Nucleophile, Ring Opening and Ring Closure) mechanism. Initially condensation of 2-(1-indolyl)-aniline and ninhydrin generates a spirocyclic intermediate 5′H-spiro[indene-2,6′-indolo[1,2-a]quinoxaline]-1,3-dione, which upon reaction with various nucleophiles like hydrazine/phenylhydrazine, amines and alcohols affords C-4 substituted indolo[1,2-a]quinoxalines in high yield (up to ~88 %) via ANRORC. The photophysical investigation shows that the quinoxaline derivatives possess significant fluorescence property with high quantum yield (QY~11.0–17.0). The N-phenylphthalazinone substituted indolo[1,2-a]quinoxaline, a molecule structurally similar to 2,2′-bipyridine system, can efficiently and selectively detect Fe²⁺ through fluorescence turn off sensing.

Herein, a selective protocol for the complete removal of acetyl protecting groups from carbohydrate derivatives based on copper nanoparticles supported on activated carbon is presented. The deacetylation procedure occurs under neutral conditions, is applicable to a wide range of substrates and tolerates a variety of functional groups (e. g. azido, allyl and silyl groups). Quantitative yields of the deacetylated product were obtained for all evaluated derivatives using catalyst amounts between 1 and 10 mol%. As a special highlight, the dual behavior of the nanocatalyst in both deacetylation and click reactions is reported.

Young people should study chemistry because it's both fun and useful. I chose my field of research because I love to be able to make precision tools using chemistry to gain understanding of, and control over, a biological system. My valuable advice from a more senior colleague at the beginning of my career was ‘a scientific path is not linear, even though it may appear to be so when the story is told afterwards'

Fluorine's high electronegativity, lipophilicity, and metabolic stability make it a valuable element for drug design and development. Consequently, significant synthetic efforts have focused on introducing fluorine and fluorinated motifs into organic molecules, with the synthesis of trifluoromethyl ketones (TFMKs) recently attracting considerable attention. Building on our ongoing research on radical organofluorine chemistry, we present herein the divergent synthesis of trifluoromethyl ketones directly from olefins using readily available chloro- and bromotrifluoroacetone as synthetic precursors of the trifluoroacetonyl radical under photoredox catalysis. Mechanistic studies revealed that the divergence is attained through radical polar crossover (RPC) and hydrogen atom transfer (HAT) mechanisms.

An efficient and scalable Buchwald-Hartwig amination towards the synthesis of the API candidate 4-((2-Chlorophenyl)amino)-6-((6-methylpyridin-2-yl)amino)nicotinamide as a JAK inhibitor was described. The process was developed using water and a water-miscible co-solvent. It was facilitated by the benign by design surfactant TPGS-750-M, that promoted the robust and reliable preparation of our target compound in high yields, with improved reaction profile and via an operationally simple protocol.