Regioselective synthesis of calix[8]crowns by direct alkylation of p- tert-butylcalix[8]arene

Article abstract of DOI:10.1016/0040-4039(96)00684-3

Direct alkylation of p-tert-butylcalix[8]arene with oligoethylene glycol ditosylates affords calix[8]crowns-n with a bridging pattern dependent on the nature of the base used. Alkali metal hydrides (NaH or KH) afford mainly 1,4- calix[8]crowns 2(n) in yield up to 46%, while K₂CO₃ and Cs₂CO₃ with triethylene glycol ditosylate give the 1,3-crown 4₄ and its 1,5-isomer 5₄ as the main product, respectively. Appreciable amounts of 1,2-calix[8]crowns 3₄ are formed with all bases but NaH. At room temperature the ¹H NMR spectra of compounds 2(n)-5₄ show broad signals indicative of hampered conformational mobility.