Deep-Cavity Calix[4]naphth[4]arene Macrocycles: Synthesis, Conformational Features, and Solid-State Structures.

We recently introduced calix[ n ]naphth[ m ]arenes as a novel class of deep-cavity hybrid macrocycles constituted by phenol (n) and naphthalene (m) units. In this study, we report the synthesis, conformational analysis, spectroscopic properties, and solid-state structures of calix[4]naphth[4]arene ( C 4 N 4 ) and its permethylated analog ( C 4 N 4 -Me ), thereby expanding the calix[ n ]naphth[ m ]arene family. C 4 N 4 was synthesized through a 2 + 2 fragment coupling macrocyclization under acidic conditions, where the solvent played a crucial role in selectively forming the C 4 N 4 derivative. The X-ray structure of C 4 N 4 reveals a chair-like 1,2,3,4-alternate conformation characterized by two opposing 3/4-cone moieties stabilized by intramolecular hydrogen bonds. In contrast, the X-ray structure of C 4 N 4 -Me exhibits a 1,3,5,7-alternate conformation.