(Trifluoromethylselenyl)methylchalcogenyl as Emerging Fluorinated Groups: Synthesis under Photoredox Catalysis and Determination of the Lipophilicity

The synthesis of molecules bearing (trifluoromethylselenyl)methylchalcogenyl groups is described via an efficient two-step strategy based on a metal-free photoredox catalyzed decarboxylative trifluoromethylselenolation with good yields up to 88 %, which raised to 98 % in flow chemistry conditions. The flow methods allowed also to scale up the reaction. The mechanism of this key reaction was studied. The physicochemical characterization of these emerging groups was performed by determining their Hansch–Leo lipophilicity parameters with high values up to 2.24. This reaction was also extended to perfluoroalkylselenolation with yields up to 95 %. Finally, this method was successfully applied to the functionalization of relevant bioactive molecules such as tocopherol or estrone derivatives.     

New series of acridines and phenanthrolines: synthesis and characterization

New series of acridines and phenanthrolines have been prepared from β-chlorovinyl aldehydes and various aniline derivatives allowing the installation of valuable substituents, such as ketone, nitro or amino groups at the heterocyclic core. X-ray analyses confirmed the structures of acridines and phenanthrolines as well as the presence of partially hydrogenated rings and their crucial impact on the overall shape of the acridine-based architectures. ¹H NMR revealed the helical behaviour of several acridine motives. Comparison of UV data between architectures and influence of number of partially hydrogenated rings is also described.     

3D Study of the Morphology and Dynamics of Zeolite Nucleation

The principle aspects and constraints of the dynamics and kinetics of zeolite nucleation in hydrogel systems are analyzed on the basis of a model Na‐rich aluminosilicate system. A detailed time‐series EMT‐type zeolite crystallization study in the model hydrogel system was performed to elucidate the topological and temporal aspects of zeolite nucleation. A comprehensive set of analytical tools and methods was employed to analyze the gel evolution and complement the primary methods of transmission electron microscopy (TEM) and nuclear magnetic resonance (NMR) spectroscopy. TEM tomography reveals that the initial gel particles exhibit a core–shell structure. Zeolite nucleation is topologically limited to this shell structure and the kinetics of nucleation is controlled by the shell integrity. The induction period extends to the moment when the shell is consumed and the bulk solution can react with the core of the gel particles. These new findings, in particular the importance of the gel particle shell in zeolite nucleation, can be used to control the growth process and properties of zeolites formed in hydrogels.     

Influence of the PVOH molar mass on the morphology and functional properties of EVOH/PVOH films prepared by melt blending

The influences of the molar mass (low, medium, and high) and content of poly(vinyl alcohol) (PVOH) dispersed by melt-blending in an ethylene vinyl alcohol (EVOH) copolymer on the morphology, microstructure, thermal, mechanical, and oxygen barrier properties were investigated. Multilayer films with external low-density polyethylene layers and inner EVOH/PVOH blend layer and respective monolayer films were elaborated and characterized. EVOH/PVOH blends exhibited a good compatibility because of the initial presence of PVOH segments in EVOH. The detailed quantitative analysis of the morphology performed for all blends showed that the finest dispersion was obtained with the PVOH with the lowest molar mass. The properties of the films as a function of the PVOH content and its molar mass were determined herein. Significant improvement of barrier properties was obtained at moderated water activities (up to a_w = 0.6) by using the PVOH with the lowest molar mass. Compared to the neat EVOH material, the oxygen permeability coefficients decreased by a factor 2 by adding 15 vol% PVOH while the thermal and mechanical properties remained similar.     

Photoredox-Catalyzed Selective Synthesis of Allylic Perfluoroalkanes from Alkenes

We report herein a novel photoredox-catalyzed synthesis of allylic trifluoromethanes. The use of sulfilimino iminium as a source of trifluoromethyl radicals proves crucial to achieving high selectivity. Importantly, both styrene derivatives and unactivated alkenes are for the first time suitable partners for this process. The mild reaction conditions are compatible with a variety of functional groups. Remarkably, this method is readily broadened to other perfluoroalkyl groups (R_F=CFCl₂, CF₂Br, C₄F₉). An extensive mechanistic study is also provided.     

Synthesis of vulpinic and pulvinic acids from tetronic acid

A common precursor, tetronic acid, was used in the synthesis of several vulpinic acids and pulvinic acids, which are pigments found in several lichens and mushrooms. The key features of this method are a two-step alkylidenation of benzyl tetronate and a Suzuki-Miyaura cross-coupling. The synthesis of several natural products, vulpinic acid, pinastric acid, xerocomic acid is described.     

Pyridylalkylamine ligands and their palladium complexes: structure and reactivity revisited by NMR

Pyridylmethylamines or pma are versatile platforms for different catalytic transformations. Five pma‐ligands and their respective Pd complexes have been studied by liquid state NMR. By comparing ¹H, ¹³C and ¹⁵N chemical shifts for each pma/pma–Pd couple, a general trend for the metallacycle atoms concerns variations of the electronic distribution at the pendant arm, especially at the nitrogen atom of the ligand. Moreover, the increase of the chemical shift of the pendant arm nitrogen atom from primary to tertiary amine is also related to the increase of crowding within the complex. This statement is in good agreement with X‐ray data collected for several complexes. Catalytic results for the Suzuki–Miyaura reaction involving the pma–Pd complexes showed within this series that a sterically crowded and electron‐rich ligand in the metallacycle was essential to reach the coupling product with a good selectivity. In this context, NMR study of chemical shifts of all active nuclei especially in the metallacycle could give a trend of reactivity in the studied family of pma–Pd complexes. Copyright © 2014 John Wiley & Sons, Ltd.