Syntheses and conformations of tetrahomodioxacalix[4]arene tetraamides and tetrathioamides

Abstract

A series of tetrahomodioxacalix[4]arene tetraamides and tetrathioamides with four p-phenyl groups on their upper rim were synthesized. From the H-1 and C-13 NMR and crystal structure, N-butylamido homooxacalix[4]arene (4) was found to be in the 1,3-alternate conformation and has intramolecular hydrogen bonding between N-H and facing oxygen atoms of the carbonyl O=C group. This hydrogen bonding decreased the metal ion complex ability. Transformation of the 1,3-alternate N-butylamido (4) into N-butylthioamido homooxacalix[4]arene (5) using Lawesson's reagent gave a conformational change to the C-1,2-alternate.