The first procedure for the selective partial O-alkylation of p-tert-butylcalix[8]arene 1 affording well defined products is described. Treatment of 1 with p-X-benzyl bromides (X = H, Me, tert-Bu, NO2, CN) and K2CO3 in THF/DMF gives the corresponding 1,3,5,7-tetrabenzyl ethers 2-6 having C4 symmetry. Their structures were firmly established by FAB(+) MS, H-1- and C-13-NMR. Variable temperature NMR studies evidenced conformational flexibility for 2-6. A possible rationale is proposed in order to explain the origin of the 1,3,5,7-substitution pattern.
Tetra-o-benzylated Calix[8]arenes With C(4) Symmetry
NERI, Placido;
1993-01-01
Abstract
The first procedure for the selective partial O-alkylation of p-tert-butylcalix[8]arene 1 affording well defined products is described. Treatment of 1 with p-X-benzyl bromides (X = H, Me, tert-Bu, NO2, CN) and K2CO3 in THF/DMF gives the corresponding 1,3,5,7-tetrabenzyl ethers 2-6 having C4 symmetry. Their structures were firmly established by FAB(+) MS, H-1- and C-13-NMR. Variable temperature NMR studies evidenced conformational flexibility for 2-6. A possible rationale is proposed in order to explain the origin of the 1,3,5,7-substitution pattern.File in questo prodotto:
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