Synthesis of Strained Macrocyclic Biaryls for Enthalpy-Driven Ring-Opening Polymerization

Abstract

Polymerizable macrocyclic biarylene−ether−ketones and biarylene−ether−sulfones are accessible from linear, bis(chloro)-terminated oligomers via nickel-catalyzed, intramolecular coupling under pseudo-high-dilution conditions. Single-crystal X-ray analyses of the resulting cyclo-oligomers reveal extremely distorted and highly strained geometries, with 4,4‘-biphenylene units showing deviations of up to 70° from linearity.

2,2′-Bipyridyl-Embedded Cycloparaphenylenes as a General Strategy To Investigate Nanohoop-Based Coordination Complexes

“…We surmised that the most general synthetic strategy leading to the 2,2′-bipyridyl-embedded nanohoops would be one that formed the pyridine–pyridine linkage in the macrocyclization step. Because of the instability of 2-pyridylboranes, , we targeted reductive couplings of pyridyl halides as the key cyclization step . Yamago recently demonstrated that reductive homocoupling of aryl bromides can be used to prepare a precursor to [5]­CPP .…”

Enthalpy-Driven Ring-Opening Polymerization of Highly Strained Macrocyclic Biaryl-Ether-Ketones

“…Determination of Macrocycle Strain-Enthalpies from Melt-Phase Polymerization. From the range of highly strained macrocycles described in the preceding paper, the ether−ketones 1 − 4 (Chart ) were selected for detailed investigation of their ring-opening polymerization chemistry. Initial DSC studies (10 °C min -1 heating rate, under nitrogen) showed that the sharp melting endotherms of these macrocycles ( T m = 354, 387, 353, and 410 °C for 1 − 4 respectively) were fully reproducible on succesive heating scans indicating that, despite their very evident ring-strain, such macrocycles are stable toward thermolytic ring-opening at temperatures exceeding 400 °C.…”

“…Macrocyclic aromatic ethers produced by nucleophilic aromatic etherification are almost invariably strain-free, as a result of the reversibility of the S N Ar reaction, and their ring-opening polymerization thus depends almost entirely on entropic effects . We have however shown in the preceding paper, and in earlier communications, , that nickel(0)-catalyzed cyclization of haloarene-terminated oligomers allows the creation of highly strained biaryl-containing macrocyclic aromatic ether−ketones and ether−sulfones. In the present paper we describe the enthalpy-driven ring-opening polymerization of such macrocycles, both in the melt and in solution, and show that the high levels of strain evident in their structures can be determined semiquantitatively in terms of the enthalpy released during ring-opening polymerization.…”

“…As outlined in the preceding paper, 1 there is considerable current interest in the synthesis of high-performance engineering thermoplastics by ring-opening polymerization of macrocyclic oligomers. 2 Such oligomers characteristically exhibit very low melt viscosities and liberate no volatile (or indeed any other) coproducts during polymerization, so that they are attractive precursors for composite materials production and for reactive fabrication of high performance polymers in general.…”

4,4′-Bis(4-fluorophenylsulfonyl)oxydibenzene

“…For details of structure-property relationships of crystalline polysulfones, see Carlier et al (1992), and for information on structure determinations of polymers from powder data, see Colquhoun et al (2003). For related structures, see for example Colquhoun et al (2005Colquhoun et al ( , 2002 and Holman et al (2001). Table 1 Hydrogen-bond geometry (Å , ).…”