Effect of aromatic-aromatic interactions on the conformational stabilities of macrocycle and preorganized structure during macrocyclization.

The crystal structures and dynamic behavior in solution of aromatic amides containing terphenyl groups were revealed by X-ray crystallographic analysis and VT-NMR measurements. Controlling the synthetic yield and molecular shape of the macrocycles with intramolecular aromatic-aromatic interactions was successfully achieved. N,N'-Diethyl-N,N'-diterphenyl-1,3-benzenedicarboxamide (2) exists in the syn conformation and two terphenyl groups are on the same side of the plane of the central benzene ring due to attractive aromatic-aromatic interactions between the two terphenyl moieties. The yield of the macrocyclization reaction of 1,3-benzenedicarboxylic acid with bis(ethylamino)terphenyl (4) was relatively high (55% yield) because an intermediate in the macrocyclization reaction was preorganized in the syn conformation, which is similar to the diamide 2. On the other hand, N,N'-diethyl-N,N'-diterphenyl-1,4-benzenedicarboxamide (3) exists in the anti conformation and two terphenyl groups are positioned on opposite sides of the plane of the central benzene ring. In contrast to the 1,3-derivative, the yield of the macrocyclization reaction of the 1,4-benzenedicarboxylic acid with the diamine 4 was low (19% yield). Although macrocycle 5 exists in a planar conformation in the crystal and in solution, macrocycle 6 exists in a twisted conformation. A deformation of the twist was induced by a tilted T-shaped aromatic-aromatic interaction between the central phenylene rings of the macrocycle.