SYNTHESIS, STRUCTURE, AND DYNAMICS OF A MACROCYCLOPHANE

The synthesis of the macrocyclophane 6 by intramolecular alkyne trimerization using Vollhardt's catalyst is presented. The construction is composed of one 1,3,5-substituted benzene and one 2,6,10-triaminotrioxatricornan subunit linked by three tetramethylene arms. The crystal structures of 5-tos/6-tos and 6 have been determined. 5-tos/6-tos shows a structure distorted from a helical C3 symmetric conformation, and 6 shows a structure of C1 symmetry with a void in the interior. Empirical force field and semiempirical calculations, and conformational analysis by H-1 NMR techniques, support a noncollapsed solution structure of 6. Low-temperature H-1 NMR of 6 reveals a dynamic behavior consistent with a stepwise flip of pitch of the tetramethylene chains.