Monofunctional hyperbranched ethylene oligomers

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WIEDEMANN, Thomas, Gregor VOIT, Alexandra TCHERNOOK, Philipp ROESLE, Inigo GÖTTKER-SCHNETMANN, Stefan MECKING, 2014. Monofunctional hyperbranched ethylene oligomers. In: Journal of the American Chemical Society. 136(5), pp. 2078-2085. ISSN 0002-7863. eISSN 1520-5126. Available under: doi: 10.1021/ja411945n

@article{Wiedemann2014-02-05Monof-27641, title={Monofunctional hyperbranched ethylene oligomers}, year={2014}, doi={10.1021/ja411945n}, number={5}, volume={136}, issn={0002-7863}, journal={Journal of the American Chemical Society}, pages={2078--2085}, author={Wiedemann, Thomas and Voit, Gregor and Tchernook, Alexandra and Roesle, Philipp and Göttker-Schnetmann, Inigo and Mecking, Stefan} }

Mecking, Stefan Monofunctional hyperbranched ethylene oligomers Roesle, Philipp Voit, Gregor 2014-04-17T11:22:58Z eng Mecking, Stefan terms-of-use Roesle, Philipp Voit, Gregor Tchernook, Alexandra Göttker-Schnetmann, Inigo Göttker-Schnetmann, Inigo 2014-02-05 Tchernook, Alexandra The neutral κ<sup>2</sup>N,O-salicylaldiminato Ni(II) complexes [κ<sup>2</sup>N,O-{(2,6-(3′,5′-R<sub>2</sub>C<sub>6</sub>H<sub>3</sub>)<sub>2</sub>C<sub>6</sub>H<sub>3</sub>-N═C(H)-(3,5-I<sub>2</sub>-2-O-C<sub>6</sub>H<sub>2</sub>)}]NiCH<sub>3</sub>(pyridine)] (1a-pyr, R = Me; 1b-pyr, R = Et; 1c-pyr, R = iPr) convert ethylene to hyperbranched low-molecular-weight oligomers (Mn ca. 1000 g mol–1) with high productivities. While all three catalysts are capable of generating hyperbranched structures, branching densities decrease significantly with the nature of the remote substituent along Me > Et > iPr and oligomer molecular weights increase. Consequently, only 1a-pyr forms hyperbranched structures over a wide range of reaction conditions (ethylene pressure 5–30 atm and 20–70 °C). An in situ catalyst system achieves similar activities and identical highly branched oligomer microstructures, eliminating the bottleneck given by the preparation and isolation of Ni–Me catalyst precursor species. Selective introduction of one primary carboxylic acid ester functional group per highly branched oligoethylene molecule was achieved by isomerizing ethoxycarbonylation and alternatively cross metathesis with ethyl acrylate followed by hydrogenation. The latter approach results in complete functionalization and no essential loss of branched oligomer material and molecular weight, as the reacting double bonds are close to a chain end. Reduction yielded a monoalcohol-functionalized oligomer. Introduction of one reactive epoxide group per branched oligomer occurs completely and selectively under mild conditions. All reaction steps involved in oligomerization and monofunctionalization are efficient and readily scalable. 2014-04-17T11:22:58Z Wiedemann, Thomas Journal of the American Chemical Society : JACS ; 136 (2014), 5. - S. 2078-2085 Wiedemann, Thomas

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