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 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 broad signals indicative of hampered conformational mobility. Copyright (C) 1996 Elsevier Science Ltd

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

NERI, Placido
1996

Abstract

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 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 broad signals indicative of hampered conformational mobility. Copyright (C) 1996 Elsevier Science Ltd
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11386/3136522
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