Grafting of functional nitroxyl free radicals to polyolefins as a tool to postreactor modification of polyethylene‐based materials with control of macromolecular architecture

Nitroxyl radicals were used as functionalizing agents during the free radical postreactor modification process of polyolefins carried out in the melt. The 4‐hydroxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl (HO‐TEMPO) and the 4‐benzoyloxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl (BzO‐TEMPO) free radicals were successfully grafted onto a polyethylene‐based material (ethylene‐co‐1‐octene copolymer) by coupling reaction with polymer macroradicals; these last were formed by H‐abstraction through peroxide addition. The macromolecular structure of the functionalized polyolefins was assessed by ¹H‐NMR, FTIR spectroscopy, and SEC measurements which were used to evidence the grafting site, to evaluate the grafting level and to highlight the occurrence of chain extension through crosslinking side reactions. Indeed the use of proper model compounds allowed the preparation of accurate FTIR calibration curves for the quantitative determination of the functionalization degree. Besides the high temperature SEC analysis highlighted that this fast and simple coupling reaction between macroradicals and nitroxyl free radicals grants the grafting of functionalities onto the polyolefin backbone by contemporarily preventing the side reactions liable of the structure and MW modification of the pristine polymer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Anisometric,non-mesogenic,tailor-made monomer for reverse-mode shutters

Reverse-mode operation films can be achieved with polymer dispersed liquid crystals by many methods. One method consists in the use of either rough or polyimide treated supports in order to induce homeotropic alignment of the initial mixture that will separate in liquid crystal and polymer rich phases. The major disadvantage is the need for mesogenic monomers to keep a good alignment of the liquid crystal after the polymerization process. In this paper we present results concerning the use of an anisometric, non-mesogenic, tailor-made monomer for the preparation of excellent reverse-mode polymer dispersed liquid crystal shutters cast on rough surfaces. The combined use of rough surfaces and non-mesogenic monomers allows us to exceed earlier limits in physical and chemical properties, cost, and device dimensions by the use of a wider class of monomer molecules.     

GPhos Ligand Enables Production of Chiral N-Arylamines in a Telescoped Transaminase-Buchwald-Hartwig Amination Cascade in the Presence of Excess Amine Donor

The combination of biocatalysis and chemocatalysis can be more powerful than either technique alone. However, combining the two is challenging due to typically very different reaction conditions. Herein, chiral N-aryl amines, key features of many active pharmaceutical ingredients, are accessed in excellent enantioselectivity (typically>99.5 % ee) by combining transaminases with the Buchwald-Hartwig amination. By employing a bi-phasic buffer-toluene system as well as the ligand GPhos, the telescoped cascade proceeded with up to 89 % overall conversion in the presence of excess alanine. No coupling to alanine was observed.     

Continuous Succinic Acid Fermentation by Actinobacillus Succinogenes: Assessment of Growth and Succinic Acid Production Kinetics

Applied Biochemistry and Biotechnology - Succinic acid is one of the most interesting platform chemicals that can be produced in a biorefinery approach. The paper reports the characterization of...     

N-Alkylation of N-arylsulfonyl-α-amino acid methyl esters by trialkyloxonium tetrafluoroborates

In this work we present the results obtained for the N-alkylation of a series of N-arylsulfonyl-α-amino acid methyl esters bearing different substituents at the 4-position of the sulfonamide aromatic ring. In particular, we compare the reactivity of these species with diazomethane and trimethyloxonium tetrafluoroborate in N-methylation processes. Diazomethylation is unsuccessful for N-arylsulfonamide derivatives containing electron-releasing groups on the aromatic ring. In these cases trimethyloxonium tetrafluoroborate is the reagent of choice for the direct and quantitative N-methylation. Further we extend our evaluation to the use of triethyloxonium tetrafluoroborate. This reagent shows to be very efficient in order to prepare N-ethyl derivatives of N-arylsulfonyl-α-amino acid methyl esters. An experimental protocol similar to that used for N-methylation with trimethyloxonium tetrafluoroborate is applied for the N-ethylation.     

Convenient Synthesis of 3,4-bis(Alkylthio) Thiophenes

A variety of symmetrically substituted 3,4-dithioether-thiophenes were prepared by the acid catalyzed nucleophilic substitution of 3,4-di(methoxy)thiophene with the appropriate thiol.