calixarenes and triptycene

Owing to the unique 3D rigid structure of triptycene, two novel expanded oxacalixarenes 5a and 5b as a pair of diastereomers were efficiently synthesized in a single step by the SNAr reaction of 2,7-dihydroxytriptycene with 2,3,5,6-tetrachloropyridine in the presence of cesium carbonate. Similarly, two pairs of other triptycene-based expanded oxaxalixaenes 7a,7b and 9a,9b could also be obtained by the SNAr reactions of 2,7-dihydroxytriptycene with 1,5-difluoro-2,4-dinitrobenzene and cyanuric chloride, respectively. The structures of the expanded oxacalixarenes were studied by NMR, MS spectra, and X-ray crystal structure analyses. It was found that the expanded oxacalixarene 9b showed a dynamic interconversion between boat and chair conformations. Moreover, we also found that the expanded oxacalixarenes 5a, 5b, and 9a could all assemble into organic tubular structures and further porous architectures in the solid state, in which chlorine bonding, such as C-Cl...Cl, C-Cl...O, and C-Cl...pi interactions, played an important role.

Topics: Anthracenes; Calixarenes; Crystallography, X-Ray; Magnetic Resonance Spectroscopy; Models, Molecular; Molecular Structure