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

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 (Nail or KH) afford mainly 1,4-caiix[8]crowns 2 n in yield up to 46%, while K2CO 3 and Cs2CO 3 with triethylene glycol ditosylate give the 1,3-crown 44 and its 1,5-isomex 54 as the main product, respectively. Appreciable amounts of 1,2-calix[8]crowns 34 are formed with all bases but Nail. At room temperature the tH NMR spectra of compounds 2n-5 4 show broad signals indicative of hampered conformational mobility.