Optically Active 2,7,10,15‐Tetrahydroxytetraphenylene: Clathrates with Both Enantiomers of 1‐Phenylethylamine and Their Stability

2,7,10,15‐Tetrahydroxytetraphenylene (THTP) was synthesized in two steps by the homo‐coupling reaction of 2,2′‐dibromo‐5,5′‐dimethoxybiphenyl. Optical resolution of racemic THTP was achieved by complexation with ( S )‐1‐phenylethylamine in toluene to afford ( S , S )‐THTP in good yield. ( R , R )‐THTP was also obtained using ( R )‐1‐phenylethylamine. In the course of these studies, ( S , S )‐THTP constituted an inclusion compound even with ( R )‐1‐phenylethylamine. Both complexes were characterized by X‐ray structural analyses and the thermal analyses (DSC and TGA). The hydrogen bonding networks of the complex with ( R )‐1‐phenylethylamine are more complicated than those of the complex with ( S )‐1‐phenylethylamine. The thermal analysis suggests that the complex with ( S )‐1‐phenylethylamine is a less stable clathrate than the complex with ( R )‐1‐phenylethylamine.