Synthesis, crystal structure and dynamic behavior of naphthalene-based calix[3]amide: Cyclic trimers of 2-alkylamino-6-naphthoic acid

Treatment of 6-amino-2-naphthoic acid with dichlorotriphenylphosphorane afforded a new naphthalene ring-based calix[3]amide in moderate yield. The macrocyclic calix[3]amide exists in an anti-form in the crystalline state and forms a channel structure along its b axis. In CDCl3 solution it exists in equilibrium between the syn- and anti-forms in solution (100:57). The energy barrier between the anti- to syn-forms was calculated to be 17.8 ± 0.2 kcal/mol.