Synthesis and NMR Conformational Studies ofp-tert-Butyldihomooxacalix[4]arene Derivatives Bearing Pyridyl Pendant Groups at the Lower Rim

Abstract

Direct O-alkylation of p-tert-butyldihomooxacalix[4]arene (1) with 2-(chloromethyl)pyridine hydrochloride and NaH in DMF provided six of the nine possible (2-pyridylmethoxy)dihomooxacalix[4]arene conformers in the cone conformation. Mono- and tetrasubstituted derivatives were obtained, as well as all four (1,2-, 1,3-, 1,4- and 2,3-) types of disubstituted compounds. The conformations and the substitution patterns were established by NMR spectroscopy (1H, 13C, COSY, NOESY and TOCSY 1D). From the same reaction, another tetrasubstituted derivative (6) in a 1,2-alternate A conformation was also isolated and characterised. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)