Functionalized Hydrocarbon Belts: Synthesis, Structure and Properties

Hydrocarbon belts have drawn great attention because of their unique structures and tantalizing properties. Although a few belts and heteroatom‐doped analogs have been synthesized, belt molecules containing non‐hexagonal rings remain rare. Herein we report the construction and application of unprecedented zigzag‐type hydrocarbon belts which contain functionalized eight‐membered rings. The synthesis features fourfold intramolecular acylation reactions of resorcin[4]arene‐derived intermediates, which affords C4‐symmetric tetrabenzobelt[4]arene[4]cyclooctatrienones. Stereoselective ketone reduction with LiAlH4 and nucleophilic addition with alkynyllithiums provide the corresponding tetrahydroxylated belts. The tetraol and its methyl ether are powerful and selective hosts to form 2 : 1 and 1 : 1 complexes with cesium ion, respectively, with binding constants up to (1.71±0.33)×1011 M−2 and (1.50±0.16)×106 M−1. In addition, enantiopure C4‐symmetric belts can emit CPL with |glum| being around 0.01. Zigzag‐type hydrocarbon belts which contain functionalized eight‐membered carbocyclic rings are synthesized by stitching up all fjords of resorcin[4]arene derivatives through fourfold intramolecular acylation reactions and subsequent transformations of ketones. They are powerful and selective hosts to capture cesium ion to form 1 : 1 and 2 : 1 host–guest complexes with binding constants being up to 1.5×106 M−1 and 1.7×1011 M−2, respectively.