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 glyc ol ditosylates affords calix[8]crowns-n with a bridging pattern depend ent 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 4(4) and its 1,5-isomer 5(4) as the main product, respectively. Appreciable amounts of 1,2-calix[8]crowns 3(4) are formed with all bases but NaH. At room temperature the H-1 NMR spectra of compounds 2(n)-5(4) show b road signals indicative of hampered conformational mobility. Copyright (C) 1996 Elsevier Science Ltd