Synthesis, Structure and Conformation of Terphenylene‐Derived Oxacalixaromatics

Oxacalix[4]aromatics comprised of terphenylene units have been synthesized by cyclooligomerization of 5′‐ tert ‐butyl‐1,1′:3′,1″‐terphenyl‐4,4″‐diol ( 1 ) and electron‐deficient meta ‐dihalogenated benzene and heterocycles. Single‐crystal X‐ray analysis revealed that oxacalix[2]terphenylene[2]pyrazine 13 adopts a chair conformation, forming a molecular cavity to trap an ethyl acetate guest molecule in the solid state. 1,3‐Alternate conformations are adopted by other oxacalix[2]terphenylene[2]aromatics ( 11 , 12 and 15 ), which form a narrow tweezer‐like molecular cavity that is incapable of encapsulating any guest molecules.