Asararenes - A family of large aromatic macrocycles

Abstract

We announce the establishment of a new family of macrocycles - the asararenes, which are based on para-methylene linked "asarol methyl ether" (1,2,4,5-tetramethoxybenzene) units. Macrocycles with 6-12 aromatic units have been synthesized and isolated in a single step from asarol methyl ether and paraformaldehyde. Even larger rings, with up to 15 asarol methyl ether units, have been observed by high-resolution mass spectrometry. Single-crystal X-ray structures of asar[6]-, asar[7]-, asar[8]-, asar[9]-, asar[10]- and asar[11]arene highlight the diverse structural features of this family of macrocycles. While the cavities of the asar[6-8]arene macrocycles are mostly filled with methoxyl groups, the asar[9]- and asar[10]arene rings contain accessible cavities and self-assemble into infinite channels filled with solvent molecules in the solid state. These solid-state structures highlight the potential of this family of macrocycles for a wide range of potential applications. Gingering up macrocycles: Asarol methyl ether (1,2,4,5- tetramethoxybenzene), a component of ginger, reacts with paraformaldehyde in the presence of BF3×OEt2 to produce a new family of macrocycles. Solid-state structures of asar[6]-, asar[7]-, asar[8]-, asar[9]-, asar[10]- and asar[11]arene shed light on the conformational behavior of this new family of potential receptors, which could find applications in materials science and the life sciences in the fullness of time. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.