Post de NuChem Sciences

les travaux pratiques de l3 chimie !

In this elegant report, a regioselective syn-addition of Ni to alkynes followed by a 1,3-metallate shift enabled by resulting activated tetraccoordinate boron centre furnished axially chiral alkenes, which previously have been studied under 1,2-metallate shift-enabled central chirality but rarely under axial chirality protocol. This work showcases the efficient synthesis of axially chiral alkenes which otherwise highlights a major low rotational barrier and flexible framework challenge. The additional design of tailored substrates or use of expensive transition metals in this regard render the strategy unattractive. However, the strategy herein raises significant interest in tetracoordinated boron species for asymmetric construction of axially chiral alkenes, featuring late-stage functionalization, diverse substrate scope tolerance under mild condition, and synthetic applications. Enantioselectivity vs ligand percent showed a positive correlation, which means that product selectivity is highly tunable.

In this month’s problem session, our scientist, Vidyavathi Patro, took us through the first enantioselective total synthesis of (-)-Hunterine A which belongs to Monoterpene Indole Alkaloid (MIA) family. The authors, Elliot F. Hicks, Kengo Inoue and Brian M. Stoltz (California Institute of Technology), used an elegant aza-cope/Mannich sequence followed by azide-olefin dipolar cycloaddition to form the C7 quaternary center and the pentacyclic ring system, respectively. Here are some name reactions and key steps of the synthesis: ·       Umpolung ylide addition of cyclopentenone onto ethyl acrylate ·       Tricky 1,4-addition of the vinyl-Grignard onto the enone in which TMSCl helps promote 1,4 addition over 1,2-addition (see paper in comment section) ·       Catalytic asymmetric desymmetrisation of a meso diketone through Noyori’s transfer hydrogenation conditions ·       Beckmann rearrangement to form the piperidine ring using thionyl chloride. ·       Convergent 1,2-addition joins a vinyl dianion nucleophile and the enantioenriched ketone ·       Aza-Cope/Mannich reaction and azide-olefin dipolar cycloaddition to complete the pentacyclic ring system. Aziridine formation via triazoline photolysis where degree of pyramidality of the nitrogens was a key factor of the reaction outcome.

analyses gravimétrie du sulfate

Paper #5: Tribochemical silica-coating or alumina blasting for zirconia bonding? A systematic review of in vitro studies. The conclusions drawn were: - The combination of tribochemical silica- coating and a silane-based primer has the potential to be an effective alternative to alumina blasting for bonding to zirconia restorations in both short- and long-term simulated aging scenarios. - However, the presence of significant methodological heterogeneity in the studies hindered the possibility of conducting a quantitative analysis of the reported results. - Most of the in vitro studies presented medium risk of bias. #systematicreview #zirconia #tribochemicalsilicacoating

📣 Je pense que cet article pourrait vous intéresser car c'est une question récurrente entre utiliser la méthode coulométrique ou la méthode volumétrique en fonction de la teneur en eau cible. N'oubliez pas aussi que Metrohm propose de la spectroscopie NIR pour la mesure de la teneur en eau que ce soit en ligne ou at-line pour un suivi de sécheur par exemple ou dans un labo CQ. La calibration sera faite en utilisant le KF comme méthode de référence et Metrohm France est à votre service pour en développer.

This paper documented the first example of Pd catalyzed asymmetric Larock isoquinoline synthesis...

Matériaux pyrotechniques courants : 18, Propriétés du fluorosilicate de sodium.

👌 ✅ Un bel exemple de ce que peut faire Materia Nova, grâce à des équipements de pointe comme le ToF-SIMS, en termes d’analyses et de compréhension des performances d’une solution développée spécifiquement pour la protection contre la #corrosion. #solgel #coatings #anticorrosion IONTOF Sylvain Desprez

Presenting our work 'Photothermal and photodynamic properties of gold nanoclusters stabilised with a peptide ligand' Royal Society of Chemistry , Nanoscience #RSCNano in #RSCPoster 2024 #RSCNano