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

The synthesis of endo-functionalized cyclic oligophenylenes in which adjacent benzene rings are perpendicular to one another is described. Annulation precursors, OH- or NH2-functionalized 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, NH2-functionalized macrocycles could bind a chiral phosphoric acid in the cavity in CDCl3 solution.


General methods
All operations were performed under air unless otherwise noted. NMR spectra for product characterization ( 1 H and 13 C) were recorded on a Bruker DPX-400 (400 MHz for 1 H and 100 MHz for 13 C) spectrometer using CDCl3 [residual CHCl3 (7.26 ppm) served as an internal standard in 1 H NMR and CDCl3 (77.0 ppm) in 13 C NMR] and dimethylsulfoxide-d6 (DMSO-d6) [residual DMSO (2.50 ppm) served as an internal standard in 1 H NMR and  in 13 C NMR] as a solvent. Chemical shifts are expressed in parts per million (ppm). IR spectra were recorded on a JASCO FT/IR-4600 (ATR). Highresolution mass analyses (MALDI + ) were performed on a JEOL JMS-S3000 SpiralTOF (MALDI TOF) mass spectrometer. GPC purification was performed on a LC-908 (Japan Analytical Industry Co., Ltd.) with JAIGEL 1HH and 2HH as purification columns.

X-ray crystallographic analysis of a crystal of 1(OMe)
Single crystals of 1(OMe) for X-ray diffraction analysis, were obtained as follows. At first, macrocycle

1(OMe)[Cl]
was prepared by the annulation of 2c and septiphenylene precursor which was prepared by using 8d as a starting material. When borylation of Cl of 1(OMe)[Cl] was examined, 1(OMe) was obtained as a byproduct. Vapor diffusion method using a chloroform solution as a good solvent and acetonitrile as a poor solvent gave colorless thin platelet single crystals of 1(OMe). The single crystal X-ray diffraction data were collected on a Rigaku R-AXIS II with IP area detector using CuKa (l = 1.54187 Å). The crystals employed in this study proved to be weakly diffracting and rapidly suffered solvent loss. The structure was solved by direct methods with SHELXT. Although the molecular structure of macrocycle including four chloroform molecules was obtained, solvent molecules could not be successfully resolved. Consequently, the PLATON/SQUEEZE procedure was applied to handle the heavily disordered solvent molecules in the cavity of the macrocycle. The refinement was performed by full-matrix least squares method of F 2 using SHELXL-2016 with anisotropic temperature factors for non-hydrogen atoms. All the hydrogen atoms were located at the calculated positions and refined with riding. One of the propyl groups of the macrocycle was disordered.

t-Bu t-Bu
Br Br OH Cl B(OH) 2
NH4Cl aq. and the organic materials were extracted with EtOAc, washed with brine, and dried over MgSO4.
NH4Cl aq. and the organic materials were extracted with EtOAc, washed with brine, and dried over MgSO4.