Go toArchive
Browse byFacets
Bookbag ( 0 )
'Conformational Isomers' in keywords
Results  2 Items
Sorted by   
Publication Year
1998 (1)
1994 (1)
1Author    G. Stalke, M. Eorge, SheldrickRequires cookie*
 Title    Neue Cyclophosphazene mit Metallen der III. Hauptgruppe als Ringbausteine  
 Abstract    Acylic silylated phosphazenes of the type HN(PR2NSiMe3)2 (1) react quantitatively with molecules MMe3 (M = Al, Ga, In) under ring formation and CH4 evolution. The ring com­ pounds N(PPh2NSiMe3)2AlMe2 (2 a) and N(PPh2NSiMe3)2InMe2 (4 a) have been investiga­ ted by X-ray structure determination. 2a and 4a crystallize in the space groups P 1 and P 3 15 respectively; they show different conformations regarding the cyclohexane framework. NMR spectroscopy of the nuclei in the chelating phosphazene ligand indicates decreasing Lewis acidity of the metal containing fragments in the series AlMe2 > GaMe2 > InMe2. 
  Reference    (Z. Naturforsch. 49b, 43—49 [1994]; eingegangen am 22. September 1993) 
  Published    1994 
  Keywords    Cyclophosphazenes, Chelating Ligands, Conformational Isomers, Lewis Acidity, 27Al NMR Spectra 
  Similar Items    Find
 TEI-XML for    default:Reihe_B/49/ZNB-1994-49b-0043.pdf 
 Identifier    ZNB-1994-49b-0043 
 Volume    49 
2Author    Ion Neda, Tjark Siedentop, Alexander Vollbrecht, Holger Thönnessen, PeterG. Jones, Reinhard SchmutzlerRequires cookie*
 Title    A New Synthesis of Tetrakis(C-methyl)octakis(hydroxyethyl)calix[4]- resorcinarene via an Ethoxy-Tethered Trimethylsiloxy Precursor  
 Abstract    The octakis(trimethylsiloxy)calix[4]resorcinarenes, 3 and 4, were synthesized by reaction of 1 and its tetrabromo derivative 2 with hexamethyldisilazane, and were found to exhibit dynamic behaviour in solution. Temperature-dependent NMR investigations confirmed the presence of at least two conformational isomers of 3 in solution. The conformation of 3 in the solid state was determined by an X-ray crystal structure analysis; the calixarene displays a boat conformation. The introduction of the ethoxy group as a spacer into the molecule of 1 was ef­ fected via its reaction with ethyl bromoacetate and subsequent reduction with lithium alu­ minium hydride forming the ethoxy-tethered C-methylcalix[4]resorcinarene 6 in an impure state. Reaction of crude 6 with hexamethyldisilazane furnished the ethoxy-tethered oc-takis(trimethylsiloxy)calix[4]resorcinarene 7; its hydrolysis led to pure 6. Calixresorcinarenes display interesting proper­ ties as materials and as complexing agents. Their use in the synthesis of cavitands and (hemi)carcerands [5], as building blocks in the preparation of phosphorus-functionalized calix[4]resorcinarenes [6], and their application as a fascinating class of container molecules [7, 8] have been described. We are now presenting the synthesis and char­ acterization in a pure state of the polyol deriva­ tive 6, related to calix[4]resorcinarene, with none of the eight hydroxy groups bonded directly to the aromatic ring system, but via OCH2CH2 groups as spacers. The synthesis of 6 in an impure state from calix[4]resorcinarene and ethylene oxide has been described [9]. No direct characterization of 6 has been reported; rather, it was converted to an octaacetate. Recently, the preparation of the C-undecyl-octakis-hydroxyethyl derivative of the latter has been described, functioning as an in­ termediate in the synthesis of macrocyclic sugar clusters [ 10]. An X-ray crystal structure determination of 3, bearing eight trimethylsiloxy groups directly bonded to the upper rim of the molecule, was con­ ducted. The results are compared with regard to conformational aspects to those of the correspond­ ing octakis(ethoxy-tethered) trimethylsiloxy deriva­ tive 7. 
  Reference    Z. Naturforsch. 53b, 841—848 (1998); received February 18 1998 
  Published    1998 
  Keywords    Calix[4]resorcinarenes, Conformational Isomers, Spacer Groups, X-Ray Data 
  Similar Items    Find
 TEI-XML for    default:Reihe_B/53/ZNB-1998-53b-0841.pdf 
 Identifier    ZNB-1998-53b-0841 
 Volume    53