Brücher, Oliver ; Bergsträßer, Uwe ; Kelm, Harald ; Hartung, Jens ; Greb, Marco ; Svoboda, Ingrid ; Fuess, Hartmut (2012)
Controlling 6-endo-selectivity in oxidation/bromocyclization cascades for synthesis of aplysiapyranoids and other 2,2,6,6-substituted tetrahydropyrans.
In: Tetrahedron, 68 (34)
doi: 10.1016/j.tet.2012.05.013
Artikel, Bibliographie
Kurzbeschreibung (Abstract)
A cascade, composed of (i) oxovanadium(V)-catalyzed oxidation of bromide by tert-butyl hydroperoxide and (ii) stereoselective 6-endo-bromocyclization, affords 3-bromo-2-aryl-2,6,6-trimethyltetrahydropyrans from styrene-type tertiary alkenols in synthetically useful yields. (E)-Alkenols add the bromo- and the alkoxy substituent anti-selectively across the double bond, indicating a bromonium ion-mechanism for the ring closure. 6-endo-control of the alkenol cyclization thereby arises from the polar effect of the aryl substituent. Two methyl substituents bound to the alkene terminus are not similarly able to favor 6-endo-cyclization, because strain arising from methyl group repulsion, as the bromonium-activated π-bond and the hydroxyl oxygen approach, directs bromocyclization of tertiary prenyl-type substrates toward tetrahydrofuran formation. A hexasubstituted bromotetrahydropyran prepared from the oxidation/bromocyclization cascade served as starting material for synthesis of racemic aplysiapyranoid A, in a sequence of free radical and polar functional group interconversion.
| Typ des Eintrags: | Artikel |
|---|---|
| Erschienen: | 2012 |
| Autor(en): | Brücher, Oliver ; Bergsträßer, Uwe ; Kelm, Harald ; Hartung, Jens ; Greb, Marco ; Svoboda, Ingrid ; Fuess, Hartmut |
| Art des Eintrags: | Bibliographie |
| Titel: | Controlling 6-endo-selectivity in oxidation/bromocyclization cascades for synthesis of aplysiapyranoids and other 2,2,6,6-substituted tetrahydropyrans |
| Sprache: | Englisch |
| Publikationsjahr: | 26 August 2012 |
| Verlag: | Elsevier Science Publishing |
| Titel der Zeitschrift, Zeitung oder Schriftenreihe: | Tetrahedron |
| Jahrgang/Volume einer Zeitschrift: | 68 |
| (Heft-)Nummer: | 34 |
| DOI: | 10.1016/j.tet.2012.05.013 |
| Kurzbeschreibung (Abstract): | A cascade, composed of (i) oxovanadium(V)-catalyzed oxidation of bromide by tert-butyl hydroperoxide and (ii) stereoselective 6-endo-bromocyclization, affords 3-bromo-2-aryl-2,6,6-trimethyltetrahydropyrans from styrene-type tertiary alkenols in synthetically useful yields. (E)-Alkenols add the bromo- and the alkoxy substituent anti-selectively across the double bond, indicating a bromonium ion-mechanism for the ring closure. 6-endo-control of the alkenol cyclization thereby arises from the polar effect of the aryl substituent. Two methyl substituents bound to the alkene terminus are not similarly able to favor 6-endo-cyclization, because strain arising from methyl group repulsion, as the bromonium-activated π-bond and the hydroxyl oxygen approach, directs bromocyclization of tertiary prenyl-type substrates toward tetrahydrofuran formation. A hexasubstituted bromotetrahydropyran prepared from the oxidation/bromocyclization cascade served as starting material for synthesis of racemic aplysiapyranoid A, in a sequence of free radical and polar functional group interconversion. |
| Freie Schlagworte: | Alkyl hydroperoxide, Bromocyclization, Bromoperoxidase model, Marine natural product, Molecular modeling, Oxidation catalysis, Stereoselective synthesis, Strain, Terpenol, Vanadium(V) complex, X-ray crystallography |
| Fachbereich(e)/-gebiet(e): | 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft > Fachgebiet Strukturforschung 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft 11 Fachbereich Material- und Geowissenschaften |
| Hinterlegungsdatum: | 23 Jan 2015 08:54 |
| Letzte Änderung: | 23 Jan 2015 08:54 |
| PPN: | |
| Sponsoren: | This work is part of Ph.D. Theses of O.B. and M.G., and was supported by the Deutsche Bundesstiftung Umwelt (DBU; grant 20007/885) and the Deutsche Forschungsgemeinschaft (grant Ha1705/8–1). |
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