Synthesis of two calix[4]arene diamide derivatives for extraction of chromium(VI)

The synthesis of four diamide derivatives of the p-tert-butylcalix[4]arenes from the reaction of 5,11,17,23-tetra-tert-butyl-25,27diethoxycarbonylmethoxy-26,28-dihydroxycalix[4]arene 2 with various primary amines were reported. The H-1 and C-13 NMR, data showed that the synthesized compounds exist in the cone conformation. The complexing properties of these compounds toward Cr2O72-/HCr2O7- anions are also studied. It has been observed that receptors 5 and 6 are better extractant than the compounds 3 and 4. The protonated alkyl ammonium form of 5 and 6 is an effective extractant for transferring HCr2O7-/Cr2O72- anions from an aqueous phase into a dichloromethane layer. (c) 2005 Elsevier Ltd. All rights reserved.