A mechanistic study on the synthesis of branched functional polyethylene through reactive co-polymer approach

The reactive co-polymer approach is one of the most promising techniques for the synthesis of functional polyolefins. Following this concept, 1-hexene and p-methylstyrene are co-polymerized in the presence of a generic Brookhart-type catalyst. The microstructures of the co-polymers imply the tendency of p-methylstyrene co-monomers to place at the end of the structural branches formed by the chain walking reaction. The molar masses of the co-polymers decrease, not only at higher levels of co-monomer but surprisingly by decreasing reaction temperature. A mechanism consisting of a highly stable η³ metal–benzyl intermediate, which is quantitatively approved by density functional theory calculations, can delicately justify all the aforementioned observations. A series of the produced co-polymers is selectively functionalized by maleic anhydride at the benzylic position of p-methylstyrene, under very mild reaction conditions. Such a reactive intermediate opens the path for the introduction of different types of functionalities in polyolefins. Namely, the grafted co-polymers were further functionalized by a triazole ring, which provides a transient supramolecular network through intermolecular hydrogen bonding.     

Design and synthesis of a magnetic hierarchical porous organic polymer: A new platform in heterogeneous phase‐transfer catalysis

Recyclable phase transfer catalysts containing magnetic nanoparticles (MNPs) have been known as a major trend towards sustainable catalysts. In this study, a novel class of magnetic porous polymer on the basis of calix[4]resorcinarene was synthesized starting from silica‐coated Fe₃O₄ core‐shell nanoparticles. This compound was found as an efficient phase transfer catalyst to the conversion of benzyl halides into benzyl azides and cyanides in good yields. The catalyst could be used at least for five consecutive cycles without appreciable loss in the catalytic activity.     

Thiourea-Catalyzed C−F Bond Activation: Amination of Benzylic Fluorides

We describe the first thiourea-catalyzed C−F bond activation. The use of a thiourea catalyst and Ti(OiPr)₄ as a fluoride scavenger allows the amination of benzylic fluorides to proceed in moderate to excellent yields. Preliminary results with S- and O-based nucleophiles are also presented. DFT calculations reveal the importance of hydrogen bonds between the catalyst and the fluorine atom of the substrate to lower the activation energy during the transition state.     

Photoinduced DNA Interstrand Cross-Linking by 1,1′-Biphenyl Analogues: Substituents and Leaving Groups Combine to Determine the Efficiency of Cross-Linker

Two series of 1,1′-biphenyl analogues with various leaving groups (L=OAc, OCH₃, OCHCH=CH₂, OCH₂Ph, SPh, SePh, and Ph₃P⁺) were synthesized. Their reactivity towards DNA and the reaction mechanism were investigated by determining DNA interstrand cross-link (ICL) efficiency, radical and carbocation formation, and the cross-linking reaction sites. All compounds induced DNA ICL formation upon 350 nm irradiation via a carbocation that was generated from oxidation of the corresponding free radicals. The ICL efficiency and the reaction rate strongly depended on the combined effect of the leaving group and the substituent. Among all compounds tested, the high ICL efficiency (30–43 %) and fast reaction rate were observed with compounds carrying a nitrophenyl group and acetate ( 2 a ), ether ( 2 b and 2 c) , or triphenylphosphonium salt ( 2 g ) as leaving groups. Most compounds with a 4-methoxybenzene group showed similar DNA ICL efficiency (≈30 %) with a slow DNA cross-linking reaction rate. Both cation trapping and free radical trapping adducts were detected in the photo activation process of these compounds, which provided direct evidence for the proposed mechanism. Heat stability study in combination with sequence study suggested that these photo-generated benzyl cations alkylate DNA at dG, dA, and dC sites.     

Convection-Flow-Assisted Preparation of a Strong Electron Dopant,Benzyl Viologen,for Surface-Charge Transfer Doping of Molybdenum Disulfide

Transition metal dichalcogenides (TMDCs) have received attention as atomically thin post-silicon semiconducting materials. Tuning the carrier concentrations of the TMDCs is important, but their thin structure requires a non-destructive modulation method. Recently, a surface-charge transfer doping method was developed based on contacting molecules on TMDCs, and the method succeeded in achieving a large modulation of the electronic structures. The successful dopant is a neutral benzyl viologen (BV⁰); however, the problem remains of how to effectively prepare the BV⁰ molecules. A reduction process with NaBH₄ in water has been proposed as a preparation method, but the NaBH₄ simultaneously reacts vigorously with the water. Here, a simple method is developed, in which the reaction vial is placed on a hotplate and a fragment of air-stable metal is used instead of NaBH₄ to prepare the BV⁰ dopant molecules. The prepared BV⁰ molecules show a strong doping ability in terms of achieving a degenerate situation of a TMDC, MoS₂. A key finding in this preparation method is that a convection flow in the vial effectively transports the produced BV⁰ to a collection solvent. This method is simple and safe and facilitates the tuning of the optoelectronic properties of nanomaterials by the easily-handled dopant molecules.     

Selective debenzylation of aromatic benzyl ethers by silica-supported sodium hydrogen sulfate

A new debenzylation of aromatic benzyl ethers by silica-supported sodium hydrogen sulfate is described. The process proceeds selectively and efficiently in good to excellent yields without affecting sensitive functional groups such as nitro, COOMe, aldehyde, ketone, and tosyl.     

Very rapid copper‐mediated atom transfer radical polymerization of benzyl methacrylate at ambient temperature

The ability to do very rapid bulk atom transfer radical polymerization (ATRP) of benzyl methacrylate using a CuX/PMDETA complex at room temperature was demonstrated in this study. The experimental conditions required to synthesize low‐ and high‐molecular‐weight poly(benzyl methacrylate) with low polydispersity are reported here. The controlled/living nature of the polymerization was demonstrated through kinetic studies, and chain‐extension studies. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1053–1057, 2004     

Palladium－catalyzed Cascade Cyclization－Coupling Reaction of Benzyl Halides with N, N－Diallylbenzoylamide

A novel type of palladium-catalyzed cascade cyclization-coupling reaction has been found. Reaction of N, N-diallylbenzoylamide 1 with benzyl halides 2 afforded the corresponding dihydropyrroles 3 in moderate to excellent yields.     

Two Benzyl Dihydroflavones from Phellinus igniarius

Two new bcnzyl dihydroflavones phelligrins A and B were isolated from the fruit body of Phellinus igniarius. Their structrues were identified as 5, 7, 4‘-trihydroxy-6-O-hydroxybenzyl-dihydroflavone and 5, 7, 4‘-trihydroxy-8-O-hydroxybcnzyldihydroflavone, respectively, by means of spectral methods.