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  • Articles: DFG German National Licenses  (2)
  • Ab initio calculations  (1)
  • EPC synthesis  (1)
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  • Articles: DFG German National Licenses  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Insights into the Staudinger Reaction: Experimental and Theoretical Studies on the Stabilization of cis-Phosphazides (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1659-1664 
    Details
    ISSN: 1434-1948
    Keywords: Phosphorus ; Iminophosphorane ; Staudinger reaction ; Heterocycles ; Ab initio calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Staudinger-model reaction H3P (1) + HN3 (2) → H3P=NH (5) + N2 (6) has been investigated at the CCSD(T)/6-31G**//MP2(Full)/6-31G* level. Primary products formed in this reaction are the phosphazides H3P=N-N=NH (3) which exist as trans and cis isomers. In contrast to some previous assumptions, cis -3is 8.2 kcal mol-1 more stable than trans -3 but decomposes rather easily into the expected products H3P=NH and N2. This decomposition can be effectively hampered by intramolecular donor-acceptor interactions as shown by calculations on model compounds as well as by experiments. Thus the reaction of a methylene-σ3,λ3-phosphanyl-σ5,λ5-phosphorane with PhN3 led to a new four-membered heterocycle containing a thermally remarkable stable cis-phosphazide moiety.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Diastereoselective Michael Additions of Chiral Imidazolidines to Trityl Enones (1992)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1992 (1992), S. 1145-1151 
    Details
    ISSN: 0170-2041
    Keywords: Enones ; Trityl enones ; Michael additions ; EPC synthesis ; Pentanols, 4,5-diamino- ; Ethylenediamine, enantiomerically pure N,N-acetals of ; Propionic acids, 2,3-diamino- ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enolates A and C of t-butyl (R)-2-t-butyl-3-methyl-4-oxo-1-imidazolidinecarboxylate (1, Boc-BMI) and of 1-t-butyl 5-methyl (2R,5S)-2-t-butyl-3-methyl-1,5-imidazolidinedicarboxylate (3) and t-butyl (R)-2-t-butyl-5-lithio-3-methyl-1-imidazolidinecarboxylate (B, from 2) add in a Michael-type reaction to trityl enones (E, 4, 5). With one exception (product 8) a single diastereoisomer is formed (≫98% ds).  -  In two cases (6, 10), the crystal structures of the products are determined by X-ray diffraction. The steric course of the reactions (the relative topicity is unlike with the enolates) is discussed and compared with that of other conversions of the same reagents.  -  The trityl groups of two adducts (8 and 9) are cleaved off by treatment with LiBH4/cat. LiBHEt3 to give diaminopentanol derivatives (12 and 13).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1992199201188
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
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