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Calixarene Carbamates
Author(s) -
König Burkhard,
Fricke Tom,
Dix Ina,
Jones Peter G.,
Thondorf Iris
Publication year - 1997
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199719971120
Subject(s) - calixarene , chemistry , conformational isomerism , isocyanate , yield (engineering) , acylation , stereochemistry , medicinal chemistry , molecule , organic chemistry , polyurethane , catalysis , materials science , metallurgy
Calixarene carbamates were obtained in good yield from the clean reaction of n ‐butyl isocyanate with para ‐ tert ‐butyl‐calix[4]‐, ‐[6]‐, and ‐[8]arenes. Whereas the two larger calixarenes remain mobile in solution upon derivatisation, para ‐ tert ‐butyl‐calix[4]arene is locked in the cone conformation. A selective triple acylation was observed with Li 2 CO 3 as base, whereas K 2 CO 3 leads to complete functionalisation of all hydroxy groups. The relative stability of all possible conformers of calix[4]arene tetracarbamate ( 1 ) was examined by force field calculations, showing the cone conformer as the most stable one. The structures of compounds 1 and 3 were investigated by X‐ray structure analysis, confirming the cone conformation for both compounds.