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The organocatalytic synthesis of substituted vinylene carbonates from benzoins and acyloins was studied using diphenyl carbonate as a carbonyl source. A range of N-Heterocyclic Carbene (NHC) precursors were screened and it was found that imidazolium salts were the most active for this transformation. The reaction occurs at 90 °C under solvent-free conditions. A wide range of substituted vinylene carbonates (symmetrical and unsymmetrical, aromatic or aliphatic), including some derived from natural products, were prepared with 20-99% isolated yields (24 examples). The reaction was also developed using thermomorphic polyethylene-supported organocatalysts as recoverable and recyclable species. The use of such species facilitates the workup and allows the synthesis of vinylene carbonates on the preparative scale (>30 g after 5 runs). [ABSTRACT FROM AUTHOR]

A range of thermomorphic polyethylene‐supported organocatalysts is prepared from N‐alkyl imidazoles and polyethylene iodide (PEI) with good yields (85–92%) and high funtionality (98–99%). The catalytic activity of these species is studied for the ring opening of epoxidized methyl oleate with CO2 to give the corresponding cyclic carbonate. The reaction is carried out at 100 °C to fully exploit the thermomorphic behavior of the organocatalysts. The optimized conditions (neat, 100 °C, and 20 bar of CO2) are applied to a range of epoxidized fatty acids, including an epoxidized rapeseed oil, to give the corresponding carbonates with good yields (75–96%). The catalyst recycling is also studied, and no significant loss of activity is observed after ten runs. The fatty carbonates are important intermediates for the preparation of non‐isocyanate polyurethanes (NIPUs). [ABSTRACT FROM AUTHOR]

An imidazolium catalyst supported on thermomorphic polyethylene (PE) was prepared from 1‐methylimidazole and polyethylene iodide (PE−I). The catalyst was characterized by 1H and 13C NMR, SEC and MALDI‐ToF mass spectrometry. Its catalytic activity was evaluated in the ring‐opening of epoxides with carbon dioxide to give cyclic carbonates under solvent‐free conditions. The catalyst proved to be active at low catalyst loading (down to 0.1 mol%) and allows the reaction to occur at low CO2 pressure (1–5 bar) and moderate temperature (100 °C). A range of terminal and internal epoxides was converted to the corresponding cyclic carbonates with high yields and selectivities. The recyclability of the catalyst was studied and no significant loss of activity was observed after 5 runs. [ABSTRACT FROM AUTHOR]

Abstract: Monofunctional or telechelic polyethylenes (PEs) carrying phosphonic acid end groups are obtained from functional PE produced by catalyzed chain growth (CCG) on magnesium. CCG is first used to produce iodo‐end‐functionalized PE (PE‐I) that is efficiently turned into phosphonate end‐functionalized PE (PE‐P(O)(OEt)2) in the presence of triethylphosphite through the Michaelis–Arbuzov reaction. A simple treatment of the resulting PE‐P(O)(OEt)2 with bromotrimethylsilane leads to the targeted phosphonic acid end‐functionalized PE (PE‐P(O)(OH)2) for the first time. Vinyl‐end‐functionalized analogs (Vin‐PE‐P(O)(OEt)2) are produced using vinyl‐end‐functionalized PE‐I (Vin‐PE‐I) recently obtained through CCG. A cross‐metathesis reaction is then employed to couple Vin‐PE‐P(O)(OEt)2 and produce after treatment with bromotrimethylsilane the corresponding unprecedented α‐ω‐(diphosphonic acid) telechelic PE ((OH)2(O)P‐PE‐P(O)(OH)2). [ABSTRACT FROM AUTHOR]

Well-defined bifunctional supported catalysts that comprise tungsten hydride moieties and Brønsted acid sites were prepared successfully. The catalysts showed outstanding activities and selectivities toward the formation of high-value-added products, 2,3-dimethylbutenes and 3,3-dimethylbutene, through a combination of the metathesis and dimerization of isobutene. The relationship between the physicochemical properties of the catalysts and their activities and selectivities indicated that isobutene conversion increased from 4 to 95 % as a function of the silica content of the silicated alumina (obtained from Sasol). Nevertheless, the selectivity toward branched hexenes showed a volcano-shaped curve that presented a maximum for the catalyst with 5 wt % silica. Therefore, the control of the support acidity by the silica loading on alumina resulted in an increase of the selectivity toward neohexene. [ABSTRACT FROM AUTHOR]

The multistep synthesis of a polyethylene-supported iridium(III)-(N-heterocyclic carbene) hydrogen/deuterium exchange catalyst was performed starting from an iodo-polyethylene obtained via catalyzed polyethylene chain growth (CCG) on magnesium. Unique thermomorphic polyethylene properties give the possibility to perform catalytic hydrogen/deuterium exchange reactions at 100 °C in the homogeneous phase with simple catalyst separation as a precipitate at room temperature. The catalytic activity of the polymer-supported catalyst was compared with that of its monomeric analogue. The catalytic studies showed that the supported catalyst exhibits similar profiles and turnover numbers as homogeneous counterparts without deactivation. [ABSTRACT FROM AUTHOR]

Iodo functionalized polyethylene (PE-I), prepared by the addition of iodine after catalyzed poly­ethylene chain growth on magnesium, is demonstrated to be an efficient macroinitiator for thermally induced, controlled free radical polymerization using dimanganese decacarbonyl (Mn2(CO)10). The free radical polymerization of methyl methacrylate is initiated by thermal homolysis of (Mn2(CO)10) at 80 °C, forming reactive manganese pentacarbonyl radical species [•Mn(CO)5] capable of activating the C−I bond of PE-I. The metal catalyzed radical generation and degenerative iodine processes yielded polyethylene- b-poly(methyl methacrylate) (PE- b-PMMA) block copolymers with relatively low dispersities. The end group functionality of the block copolymer is confirmed by the successful thermal polymerization of styrene by using PE- b-PMMA as a macro­initiator in the described process. This work conclusively provides a new approach for combining polyethylene with vinyl polymers via manganese chemistry in a simple and efficient pathway of importance in synthetic polymer chemistry and other related applications. [ABSTRACT FROM AUTHOR]

Iodo functionalized polyethylene (PE-I), prepared by the addition of iodine after catalyzed poly­ethylene chain growth on magnesium, is demonstrated to be an efficient macroinitiator for thermally induced, controlled free radical polymerization using dimanganese decacarbonyl (Mn2(CO)10). The free radical polymerization of methyl methacrylate is initiated by thermal homolysis of (Mn2(CO)10) at 80 °C, forming reactive manganese pentacarbonyl radical species [•Mn(CO)5] capable of activating the C−I bond of PE-I. The metal catalyzed radical generation and degenerative iodine processes yielded polyethylene- b-poly(methyl methacrylate) (PE- b-PMMA) block copolymers with relatively low dispersities. The end group functionality of the block copolymer is confirmed by the successful thermal polymerization of styrene by using PE- b-PMMA as a macro­initiator in the described process. This work conclusively provides a new approach for combining polyethylene with vinyl polymers via manganese chemistry in a simple and efficient pathway of importance in synthetic polymer chemistry and other related applications. [ABSTRACT FROM AUTHOR]

The insertion of an olefin into a preformed metal-carbon bond is a common mechanism for transition-metal-catalyzed olefin polymerization. However, in one important industrial catalyst, the Phillips catalyst, a metal-carbon bond is not present in the precatalyst. The Phillips catalyst, CrO3 dispersed on silica, polymerizes ethylene without an activator. Despite 60 years of intensive research, the active sites and the way the first CrC bond is formed remain unknown. We synthesized well-defined dinuclear CrII and CrIII sites on silica. Whereas the CrII material was a poor polymerization catalyst, the CrIII material was active. Poisoning studies showed that about 65 % of the CrIII sites were active, a far higher proportion than typically observed for the Phillips catalyst. Examination of the spent catalyst and isotope labeling experiments showed the formation of a Si-(μ-OH)-CrIII species, consistent with an initiation mechanism involving the heterolytic activation of ethylene at CrIIIO bonds. [ABSTRACT FROM AUTHOR]

Ein funktionelles Kettentransferreagens, Bis(10 ‐ undecenyl)magnesium, wurde als Cokatalysator von [(C5Me5)2NdCl2Li(OEt2)2] eingesetzt, um das Kettenwachstum von Polyethylen (PE) an Magnesium zu katalysieren. Vinyl ‐ PE ‐ Mg ‐ PE ‐ Vinyl ‐ Einheiten wurden dann weiter funktionalisiert. Dies ist das erste Beispiel für eine katalytische Ethylenpolymerisation mit einstufiger, in situ ablaufender Funktionalisierung zu telechelen Polyethylenen. [ABSTRACT FROM AUTHOR]

The article offers information regarding facile and reproducible preparation of a well-defined bimetallic Pt3Sn catalyst using room temperature self-assembly. It mentions that the material was fully characterized and very selective in the classical isobutane dehydrogenation reaction. It presents the use of bimetallic Pt-X heterogeneous catalysts in the petrochemical industry and fuel-cell technology.