Issue 5, 2016

Dynamic helical cyclophanes with two quadruply-bridged planes arranged in an “obverse and/or reverse” relation

Abstract

We describe the design of two types of cyclophanes that generate dynamic helicity through the twisting of two planes in a clockwise or counterclockwise direction to give (M)- or (P)-helicity. We used a rectangular and anisotropic plane of 1,2,4,5-tetrakis(phenylethynyl)benzene (TPEB), since it can be stacked in pairs in two ways, in parallel or orthogonally, to be identified as distinct cyclophane molecules. We adopted a synthetic strategy for obtaining these two cyclophanes as a mixture using a macrocyclic intermediate that possessed two rotatable phenyl rings. We introduced necessary parts into the rotators to give a mixture of rotational isomers leading to a parallel or orthogonal arrangement of TPEBs, and then doubly bridged two planes of TPEB to form quadruply-bridged cyclophanes. We consider that such two planes in each cyclophane are in an “obverse and/or reverse” relation. In each cyclophane, we found unique dynamic helical forms with (M)- or (P)-helicity as well as an inherently non-chiral form. Normally, the screw-sense preference of dynamic helicity would be controlled through the intramolecular or supramolecular transmission of central chirality, when a chiral auxiliary is attached to the cyclophanes or a chiral guest is allowed to form a complex with the cyclophanes. In a case where two different substitution groups were used on bridging units to generate planar chirality in each cyclophane, the screw-sense preference was controlled through the arrangement of these substitution groups, and did not depend on the transmission of central chirality. Two different substitution groups desymmetrize the enantiomeric forms with (M)- or (P)-helicity generated in each dynamic helical cyclophane so that two dynamic helical forms with (M)- or (P)-helicity can be in a diastereomeric relation. Thus, a particular screw sense of dynamic helicity can be preferred, regardless of whether or not the two substitution groups possess some chiral element.

Graphical abstract: Dynamic helical cyclophanes with two quadruply-bridged planes arranged in an “obverse and/or reverse” relation

Supplementary files

Article information

Article type
Edge Article
Submitted
04 Dec 2015
Accepted
29 Jan 2016
First published
29 Jan 2016
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2016,7, 3240-3247

Author version available

Dynamic helical cyclophanes with two quadruply-bridged planes arranged in an “obverse and/or reverse” relation

R. Katoono, S. Kawai and T. Suzuki, Chem. Sci., 2016, 7, 3240 DOI: 10.1039/C5SC04673D

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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