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
    C2-Symmetrical Pyrrolidine Derivatives Chiral Auxiliaries in Radical Chemistry (1993)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 76 (1993), S. 441-450 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fumaramides 3b and 3c bearing the C2-symmetrical pyrrolidine moieties (2R,5R)-2,5-bis(methoxymethyl)pyrrolidine (2b) or 1,3:4,6-di-O-benzylidene-2,5-dideoxy-2,5-imino-L-idit (2c), respectively, as a chiral auxiliary lead to high diastereoselectivities in radical reactions (‘tin method’;Scheme 1). Removal of the chiral auxiliaries affords the corresponding alkylated fumaric acids Scheme 2. Single-crystal X-ray structures of 3b and 3c support arguments that lead to the model of 1,4-stereoinduction.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19930760128
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Synthesis and Reactivity of a p-Methoxyphenyl-Substituted Enediyne. A Case of Electronic Influence on the Rate of the Bergman Cycloaromatization (1992)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1992 (1992), S. 855-861 
    Details
    ISSN: 0170-2041
    Keywords: Enediynes ; 1,5 Diynes ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bicyclo[7.3.1]diynes 19a and 19b were prepared by using dibromo olefin 11 and ketone 12 as building blocks. The key step of the synthetic sequence is an intramolecular Nicholas reaction of 17 to give the bicyclo[7.3.1]diyn-10-one dicobalthexacarbonyl adducts 18a and 18b (66% total yield). Oxidative decomplexation of 18a and 18b with cer(IV) ammonium nitrate gave the diynes 19a and 19b, respectively. Both diynes 19a and 19b could be oxidatively converted into the enediyne 20 by using DDQ. In contrast to the unsubstituted enediyne 4, compound 20 can be isolated at room temperature Quantitative kinetic measurements of the rate of the Bergman cyclization of 20 gave ΔG# (37°C) = 111 kJ mol-1. This value is 12.3 kJ mol-1 higher than that of 4. The difference in the free activation energy between 20 and 4 is attributed to electronic effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1992199201140
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Diastereoselectivity in the halolactonization of 2-alkoxy-4-alkenoic acids and-4-alkenamides (1990)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1990 (1990), S. 323-330 
    Details
    ISSN: 0170-2041
    Keywords: 1,3-Asymmetric induction ; Butyrolactones ; Halolactonization ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Iodolactonization of 2-alkoxy- and 2-hydroxy-4-alkenoic acids 3a-d under kinetic control gives mixtures of cis- and trans-lactones 6a-d and 7a-d with cis-selectivity up to 5.5:1.0. The bromolactonization of carboxamides 4 a, 4 c, and 5 c shows moderate 1,3-asymmetric induction, favoring the trans-lactones 9 with a selectivity of up to 2.5:1.0.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199019900161
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Synthesis of 11-Membered Enediyne Ketones by the Intramolecular Nicholas Reaction (1993)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 1009-1016 
    Details
    ISSN: 0170-2041
    Keywords: Enediynes ; Nicholas reaction ; Macrocycles ; Eleven-membered rings ; Calculations, force-field ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An efficient route to 11-membered enediyne ketones 13 and 22 was developed. This route is based on an intramolecular Nicholas reaction of 11 and 20, respectively. In the course of the preparation of the cyclization substrates 11 and 20, it was important to use the acetylenic alcohols 6 and 15 as building blocks for the construction of the cis-enediynes 8 and 17, respectively, instead of the corresponding ketones which were converted into unstable acyclic enediynes. Some transformations of enediyne ketone 22 were also studied. For example, 22 could be transformed into the 2-formyl compound 26 via the silyl enol ether 24. In addition, 24 was used for the preparation of the 2-amino ketone 29.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1993199301160
    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...