Tetra-O-benzylated Calixarenes with C4 Symmetry

Article abstract of DOI:10.1016/S0040-4039(00)73693-8

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, 1H- and 13C-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. Key words: calix<8>arenes, tetraalkylation, 1,3,5,7-tetrabenzyl ethers, C₄ symmetry.