ISSN:
1573-1111
Schlagwort(e):
Calixarenes
;
preparation
;
conformation
;
dynamics
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
Notizen:
Abstract The pyrolysis of several dialkylphosphate ester derivatives of calix[4]arenes yielded the same phosphorus bridged compound7. Under the pyrolytic conditions the phosphate groups may be cleaved or intermolecularly transferred. X-ray crystallography of the bridged calixarenes7 and8 shows that they exist in a chiral ‘flattened cone’ (fc) conformation. The bridged calixarenes undergo in solution a dynamic process with a barrier of about 10.1 kcal mol−1 for7 and8 and 13.1 kcal mol−1 for10, respectively. The dynamic processes result in enantiomerization of the systems. Pyrolysis of partially phosphorylated calix[6]arenes resulted in the formation of two products (11 and12), each consisting of two subunits of three proximal rings bridged by a phosphate group. The rotational barriers for11 and12 are 14.4 and 8.8 kcal mol−1, indicating that the bridged calix[6]arene system12 is appreciably more flexible than11.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00708985
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