376387-68-7Relevant articles and documents
Competition between the donor and acceptor hydrogen bonds of the threads in the formation of [2]rotaxanes by clipping reaction
Martins, Marcos A. P.,Zimmer, Geórgia C.,Rodrigues, Leticia V.,Orlando, Tainára,Buriol, Lilian,Alajarin, Mateo,Berna, Jose,Frizzo, Clarissa P.,Bonacorso, Helio G.,Zanatta, Nilo
, p. 13303 - 13318 (2017/11/27)
The synthesis of benzylic amide [2]rotaxanes using 1,2-bis(aminocarbonyl-(1′-tert-butyl-1H-pyrazole-[3′]5′-yl))-ethanes as templates is reported. These templates are equipped with tert-butyl pyrazole-based stoppers and have donor (N-H) and acceptor (CO) hydrogen bond groups. The synthesis of [2]rotaxanes has been shown to be highly dependent on the tert-butylpyrazole stoppers. While the thread with 1′,3′-disubstituted pyrazoles as stopper units was shown to be an excellent template for the synthesis of [2]rotaxanes, the thread with 1′,5′-disubstituted pyrazoles as stopper units did not yield the expected [2]rotaxane. The structure of the synthesized [2]rotaxanes was characterized using NMR experiments and X-ray diffraction, with the latter showing that the macrocycle adopts a distorted chair conformation. An in-depth study of the isolated thread's X-ray structures and concentration-dependent NMR experiments seem to explain the dependence of the rotaxane formation on the substitution pattern of the thread's pyrazole stoppers.
