Issue 9, 2016

A chiral “Siamese-Twin” calix[4]pyrrole tetramer


We describe our results in the attempted template syntheses of oligomacrocycle calix[4]pyrrole dimer 4, using Hay coupling reaction conditions, tetraalkynyl calix[4]pyrrole 5 as starting material and two bipyridyl N-oxides of different length as templates. We found that the short bis-N-oxide 3 was not an efficient template for the macrocyclization reaction producing an insoluble crude reaction mixture containing exclusively oligomerization and polycondensation products. On the other hand, when we used the long bis-N-oxide 6 as template we obtained a soluble crude reaction mixture in which we did not detect the expected calix[4]pyrrole dimer 4. Instead, we isolated, in low yield, an encapsulation complex of the bis-N-oxide 6 in a partially reacted calix[4]pyrrole dimer. The major isolated species was an unprecedented calix[4]pyrrole tetramer encapsulating two molecules of 6. The complex adopted a chiral helical-like conformation in the solid state resembling the previously described so-called “Siamese-Twin porphyrins”.

Graphical abstract: A chiral “Siamese-Twin” calix[4]pyrrole tetramer

Supplementary files

Article information

Article type
Edge Article
27 Apr 2016
26 May 2016
First published
26 May 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-NC license

Chem. Sci., 2016,7, 5976-5982

Author version available

A chiral “Siamese-Twin” calix[4]pyrrole tetramer

A. Galán, G. Aragay and P. Ballester, Chem. Sci., 2016, 7, 5976 DOI: 10.1039/C6SC01843B

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