Spontaneous Helix Formation of “meta”-Ethynylphenol Oligomers by Sequential Intramolecular Hydrogen Bonding inside the Cavities

Abstract

Phenol-based oligomers linked with acetylenes at their meta positions, " meta"-ethynylphenol oligomers, were developed as a synthetic helical foldamer. The architecturally simple oligomers spontaneously formed helical higher-order structures by sequential intramolecular hydrogen bonds through the multiple phenolic hydroxy groups inside the cavities. The hydrogen bonds forced C-C≡C-C bond angles to largely bend toward the inside. Addition of chiral amines caused the helices to be chiral by electrostatic interactions between the resulting chiral ammonium cations and the phenolate anions.

A Pyridine‐Acetylene‐Aniline Oligomer: Saccharide Recognition and Influence of this Recognition Array on the Activity as Acylation Catalyst

“…This difference from the precursors probably results from spontaneous helix formation of 2 . Similar length‐dependence has been reported for other oligo(arylene ethynylene)s to form helical higher‐order structures [9a] . Spontaneous helix formation of 2 can be interpreted to result from that the cisoid conformation of pyridine‐acetylene‐aniline units is more stable than the transoid one.…”

Preferential Recognition and Extraction to Pentoses over Hexoses by a D6h-Symmetrical Ethynylphenol Macrocycle with Six Inner Phenolic Hydroxy Groups

“…Trimer building blocks 4 and 5 were synthesized according to literature methods. 1 Macrocyclization was carried out by Sonogashira reaction of 4 and 5 under a diluted condition, affording 2-MOM in an acceptable yield even though six MOM groups must stuff into the hole. The MOM protons of 2-MOM were much deshielded due to field effects from the oxygen atoms of the closely positioned MOM groups (Figure 5).…”

“…Tetrahydrofuran (THF) was freshly distilled from sodium benzophenone ketyl before use. Four starting materials, 1,3-bis­{[3-iodo-2-(methoxymethoxy)-5-pentylphenyl]­ethynyl}-2-(methoxymethoxy)-5-pentylbenzene ( 4 ), 1,3-bis­{[3-ethynyl-2-(methoxymethoxy)-5-pentylphenyl]­ethynyl}-2-(methoxymethoxy)-5-pentylbenzene ( 5 ), and 1,1′-(1,2-ethynediyl)­bis­[3-(2-{3-(2-{3-iodo-2-(methoxymethoxy)-5-pentylphenyl}­ethynyl)-2-(methoxymethoxy)-5-pentylphenyl}­ethynyl)-2-(methoxymethoxy)-5-pentylbenzene] ( 6 ) were prepared by the procedures in the literature …”

“…Very recently, we developed linear oligomers 1 consisting of multiple phenol rings linked with acetylene bonds (Figure 1 top). 1 Because the phenolic hydroxy group can work as a hydrogen-bonding acceptor as well as a donor, 1a spontaneously formed helical higher-order structures by sequential intramolecular hydrogen-bonding between the adjacent phenolic hydroxy groups. In these helical structures, the acetylene bonds bent inward the holes of helices as a result of the hydrogen bonds formed on a priority basis.…”

Metal-Mediated Coordination Cages: Endohedral Functionalization and Oligonucleotide Embedding

“…In literature similar systems have been synthesized succesfully without mentioning any synthetic problems. [210,211] However, the side product could be identified as intramolecular cyclization product, resulting in the asymmetric benzofuran containing ligand (32). With an alternative synthesis route, the desired ligand 31 could be obtained, but it converted in presence of water directly to the intramolecular cyclized ligand, which made this system impractical for the intended application.…”