Rim-Differentiated C(5)-Symmetric Tiara-Pillar[5]arenes

[Image: see text] The synthesis of “rim-differentiated” C(5)-symmetric pillar[5]arenes, whose two rims are decorated with different chemical functionalities, has remained a challenging task. This is due to the inherent statistical nature of the cyclization of 1,4-disubstituted alkoxybenzenes with different substituents, which leads to four constitutional isomers with only 1/16th being rim-differentiated. Herein, we report a “preoriented” synthetic protocol based on FeCl(3)-catalyzed cyclization of asymmetrically substituted 2,5-dialkoxybenzyl alcohols. This yields an unprecedented 55% selectivity of the C(5)-symmetric tiara-like pillar[5]arene isomer among four constitutional isomers. Based on this new method, a series of functionalizable tiara-pillar[5]arene derivatives with C(5)-symmetry was successfully synthesized, isolated, and fully characterized in the solid state.