Bibliothek

feed icon rss

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
Filter
  • 2H-1,2-Thiazete 1,1-dioxides  (1)
  • Diaminothioketene S,S-dioxide  (1)
  • Epoxides, regioselective cleavage of  (1)
  • 1
    ISSN: 0009-2940
    Schlagwort(e): Cyclopropyl building blocks ; Strained compounds ; [4 + 2] Cycloaddition ; Regioselectivity ; Epoxides, regioselective cleavage of ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 1-Ethoxy- (8a) and 1-(trimethylsilyloxy)-1,3-pentadiene (8b) cycloadded to 2-chloro-2-cyclopropylideneacetate 6 to give low yields of endo/exo-9a and -9b, respectively. On the other hand, furans 5a-d added 6 (5b and 5d reacted regioselectively) to afford mixtures of the corresponding [4 + 2] cycloadducts endo-11a-d and exo-11a-d in good to high yields. 2-Methyl-5-(trimethylsilyloxy)furan (5e) yielded a mixture of the four cycloadducts endo/exo-11e and endo/exo-12e, which upon attempted purification on silica gel underwent facile hydrolysis to give bicyclic hemiacetals endo/exo-13 and 4-hydroxycyclo-2-hexen-1-ones endo/exo-14, respectively. Similarly endo/exo-11f, and endo/exo-12f, obtained from 2-methoxy-5-methylfuran (5f) and 6, upon hydrolysis in the presence of silica gel gave endo/exo-13 and endo/exo-14 respectively. The structures of endo-14 and exo-12f were established by X-ray crystallography. In the presence of florisil, the epoxides endo-and exo-16 were formed from trimethylsilyloxy-substituted cycloadducts endo/exo-11e. Selective reduction of the α-chlorocarboxylate functionality in the cycloadducts endo-11a-d,f with LiBH4, followed by base-catalyzed cyclization of the resulting chlorohydrins endo-21a-d, f yielded the corresponding epoxides endo-22a-d,f in 22-73% overall yield. Under identical conditions, the cycloadducts exo-11a-f could not be reduced to the corresponding chlorohydrins exo-21a-f. Regioselective reduction of the acetal epoxide endo-22f to the tertiary alcohol endo-23f was achieved with sodium dihydrobis(2-methoxyethoxy)aluminate (Red-Al®). On stirring with moist silica gel, the bicyclic acetals endo-22d,f and endo-23f cleanly hydrolysed to the highly substituted spiro[2.5]oct-6-en-5-ones endo-24d,f (26 and 24% overall yields, respectively, in four steps from 5d,f and 6) and endo-25f, respectively (23% overall yield in five steps from 5f and 6).
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 2
    ISSN: 0947-3440
    Schlagwort(e): [2 + 2] Cycloadditions ; 2H-1,2-Thiazete 1,1-dioxides ; Amidinosulfenes, in situ formation of ; Diaminothioketene S,S-dioxide ; 1,3-Dithietane 1,1,3,3-tetraoxide ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: N-Sulfonylalkylamines 2a, b react with ynamines 3 to give primarily 2H-1,2-thiazete 1,1-dioxides 4. But, except for the 4-triphenylsilyl species 4a, b, these products are unstable and undergo electrocyclic ring opening to very reactive amidinosulfenes 5, which are transformed into different products, depending on the ynamine substituents R2. The 1,3-dithietane 1,1,3,3-tetraoxide 8 is formed from N-sulfonylisopropylamine (2a) and the trimethylsilyl-substituted ynamine 3b via amidinosulfene 5c and probably thioketene S,S-dioxide 7. On the other hand, (isopropylamidino)sulfene 5d dimerizes to the 2H-1,5,2-dithiazine 9 and also gives the [2 + 4] cycloadducts 10a, 11a by reaction with 2a and ynamine 3c, respectively. In contrast, it was possible to trap phenyl-substituted amidinosulfenes 5e-h by addition of water or methanol.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...