Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Reactions of N-sulfonylalkylamines with ynamines  -  formation of 2H-1,2-thiazete 1,1-dioxides, novel thioketene S,S-dioxide dimers, and other s,n-heterocycles (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1795-1800 
    Details
    ISSN: 0947-3440
    Keywords: [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
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1995199510251
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    New Cyclopropyl Building Blocks for Organic Synthesis, 21. Diels-Alder Reactions of Methyl 2-Chloro-2-cyclopropylideneacetate with Electron-Rich Dienes: Synthesis of Potential Intermediates for Illudin M (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 1051-1064 
    Details
    ISSN: 0009-2940
    Keywords: Cyclopropyl building blocks ; Strained compounds ; [4 + 2] Cycloaddition ; Regioselectivity ; Epoxides, regioselective cleavage of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270614
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...