Restricted rotation of tert-butyl groups in sterically crowded methylene-functionalized calix[4]arenes.
The crowded methylene-functionalized calix[4]arenes 4 and 5 display restricted rotation of the tert-butyl substituents at the bridges. At low temperatures, separate signals were observed for the methyls of these groups in the (1)H NMR spectra.
Kuno
Lev
L
Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
Biali
Silvio E
SE