Conformational control in the synthesis of mixed tetraethers of calix[4]arene. Part 2

Article abstract of DOI:10.1016/S0040-4020(97)10078-3

A series of mixed tetraethers of calix[4]arene and p-tert- butylcalix[4]arene in which two distal substituents are methyl and the other two 1-alkenyl groups with 3, 4 and 5 carbon atom chains have been prepared by two routes which differ in the order in which the groups (methyl or alkenyl) were introduced. The ethers of p-tert-butylcalix[4]arene were isolated as a mixture of cone (minor) and partial cone (major) conformations in dynamic equilibrium. For die ethers of calix[4]arene the conformational outcome depended on the method of synthesis. Up to three conformations could be detected: a cone, a partial cone with an anisyl unit inverted, and a partial cone with an alkenyl-bearing ring inverted. ¹H NMR analysis of the complexes formed between these ethers and alkali metal iodides showed that both cone and partial cone complexes of the p-tert-butylcalix[4]arene tetraethers could be detected with lithium iodide, but only cone complexes with the calix[4]arene derivatives. Sodium iodide complexes were also formed with both sets of compounds but in all cases only the cone complex was detected.