Eske, Angelika, Goldfuss, Bernd ORCID: 0000-0002-1814-8818, Griesbeck, Axel G., de Kiff, Alan, Kleczka, Margarethe, Leven, Matthias, Neudoerfl, Joerg-M. and Vollmer, Moritz (2014). Ene-Diene Transmissive Cycloaddition Reactions with Singlet Oxygen: The Vinylogous Gem Effect and Its Use for Polyoxyfunctionalization of Dienes. J. Org. Chem., 79 (4). S. 1818 - 1830. WASHINGTON: AMER CHEMICAL SOC. ISSN 1520-6904
Full text not available from this repository.Abstract
The singlet oxygen reactivities and regioselectivities of the model compounds 1b-d were compared with those of the geminal (gem) selectivity model ethyl tiglate (1a). The kinetic cis effect is k(E)/k(Z) = 5.2 for the tiglate/angelate system 1a/1a' without a change in the high gem regioselectivity. Further conjugation to vinyl groups enabled mode-selective processes, namely, [4 + 2] cycloadditions versus ene reactions. The site-specific effects of methylation on the mode selectivity and the regioselectivity of the ene reaction were studied for dienes 1e-g. A vinylogous gem effect was observed for the gamma,delta-dimethylated and alpha,gamma,delta-trimethylated substrates 1h and 1i, respectively. The corresponding phenylated substrates 1j-1 showed similar mode selectivity, as monomethylated 1j exhibited exclusively [4 + 2] reactivity while the tandem products 12 and 14 were isolated from the di- and trimethylated substrates 1k and 1l, respectively. The vinylogous gem effect favors the formation of 1,3-dienes from the substrates, and thus, secondary singlet oxygen addition was observed to give hydroperoxy-1,2-dioxenes 19 and 20 in an ene-diene transmissive cycloaddition sequence. These products were reduced to give alcohols (16, 17, and 18) or furans (24 and 25), respectively, or treated with titanium(IV) alkoxides to give the epoxy alcohols 26 and 27. The vinylogous gem effect is rationalized by DFT calculations showing that biradicals are the low-energy intermediates and that no reaction path bifurcations compete.
Item Type: | Journal Article | ||||||||||||||||||||||||||||||||||||
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URN: | urn:nbn:de:hbz:38-445725 | ||||||||||||||||||||||||||||||||||||
DOI: | 10.1021/jo5000434 | ||||||||||||||||||||||||||||||||||||
Journal or Publication Title: | J. Org. Chem. | ||||||||||||||||||||||||||||||||||||
Volume: | 79 | ||||||||||||||||||||||||||||||||||||
Number: | 4 | ||||||||||||||||||||||||||||||||||||
Page Range: | S. 1818 - 1830 | ||||||||||||||||||||||||||||||||||||
Date: | 2014 | ||||||||||||||||||||||||||||||||||||
Publisher: | AMER CHEMICAL SOC | ||||||||||||||||||||||||||||||||||||
Place of Publication: | WASHINGTON | ||||||||||||||||||||||||||||||||||||
ISSN: | 1520-6904 | ||||||||||||||||||||||||||||||||||||
Language: | English | ||||||||||||||||||||||||||||||||||||
Faculty: | Faculty of Mathematics and Natural Sciences | ||||||||||||||||||||||||||||||||||||
Divisions: | Faculty of Mathematics and Natural Sciences > Department of Chemistry > Institute of Organic Chemistry | ||||||||||||||||||||||||||||||||||||
Subjects: | no entry | ||||||||||||||||||||||||||||||||||||
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Refereed: | Yes | ||||||||||||||||||||||||||||||||||||
URI: | http://kups.ub.uni-koeln.de/id/eprint/44572 |
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