Synthesis and solid state structure of oxacalix[4]arenes bearing four nitro groups and four tert-butyl groups at their extra-annular positions

Four oxacalix[4]arene derivatives, in which 1,3-dinitrobenzene units and 13-di-tert-butylbenzene units are incorporated in alternating order, were synthesized by aromatic nucleophilic substitution. The introduction of the tert-butyl groups increased the stability of the macrocycles against nucleophilic C-O bond cleavage. X-ray crystal structure analyses reveal that the oxacalixarenes adopt an unsymmetrical 13-alternate conformation. The bulky substituents did not disturb the conjugation between the bridging oxygen atoms and the dinitrobenzene rings. (C) 2009 Elsevier Ltd. All rights reserved,