Endo-Functionalized Cyclic Oligophenylenes: Synthesis and Complexation with a Chiral Phosphoric Acid

Abstract

The synthesis of endo-functionalized cyclic oligophenylenes in which adjacent benzene rings are perpendicular to one another is described. Annulation precursors, OH-or NH 2functionalized quinquephenyl diboronic acids, and septiphenyl dibromo compounds were systematically prepared by using a diprotected biphenyl-3,4′-diyl diboronic acid as a key compound. Four endo-functionalized cyclic oligophenylenes were synthesized by annulation of the precursors in dilute conditions through Suzuki−Miyaura cross-coupling. X-ray analysis of the macrocycle revealed the unique 1D channel packing structure formed by connecting the nanometer-sized cavity of the macrocycle. Furthermore, NH 2 -functionalized macrocycles could bind a chiral phosphoric acid in the cavity in CDCl 3 solution.

Reversible Adsorption of Ammonia in the Crystalline Solid of a CO2H-Functionalized Cyclic Oligophenylene

“…Cyclic oligophenylene 1a was synthesized by oxidizing cyclic 1b , a precursor that bears two CHO groups (Scheme ). According to a previously reported method, the two precursors of 1b , quinquephenyl diboronic ester 2a and dibromoseptiphenyl 3a , were prepared using diprotected biphenyl-3,4′-diyl diboronic ester 4 (Scheme a). Suzuki coupling of 2,6-dibromobenzaldehyde with 4 furnished the corresponding quinquephenyl compound in 86% yield, and a subsequent exchange of the boronic-acid protecting group from 1,8-diaminonaphthalene (dan) to pinacol (pin) afforded precursor 2a in 95% yield.…”

“…The high stability to acids and bases under wet conditions, which is often a problem with framework-type adsorbents, is a practical advantage of cyclic 1 consisting only of biphenyl bonds. Furthermore, the nm-sized inner space of the rigid cyclic 1 can be functionalized by two identical or different functional groups . The use of cyclic 1 , endo -functionalized with various functional groups is expected to allow development of materials that show high guest selectivity and high binding affinity for highly reactive gases.…”

“…Recently, we have reported endo -functionalized cyclic oligophenylene 1 , where the p -phenylene and m -phenylene units are connected in an alternating fashion (Figure a) . One of the distinguishing features of cyclic 1 is that the nm-sized aromatic cavity can be modified with one or two endohedral functional groups.…”