Threading of an Inherently Directional Calixarene Wheel with Oriented Ammonium Axles

The threading of monostoppered alkylbenzylammonium axles 7 + and 8 + with the calix[6]-wheel 3 can occur by both routes of entering the macrocycle 3 in the cone conformation: passage through the upper rim and the through the lower rim. Thus, under thermodynamic conditions, with both the axles 7 + an...

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Bibliographic Details
Published in:Journal of organic chemistry 2017-09, Vol.82 (17), p.8973-8983
Main Authors: La Manna, Pellegrino, Talotta, Carmen, Gaeta, Carmine, Soriente, Annunziata, De Rosa, Margherita, Neri, Placido
Format: Article
Language:English
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Summary:The threading of monostoppered alkylbenzylammonium axles 7 + and 8 + with the calix[6]-wheel 3 can occur by both routes of entering the macrocycle 3 in the cone conformation: passage through the upper rim and the through the lower rim. Thus, under thermodynamic conditions, with both the axles 7 + and 8 + , the two possible orientations of calix[2]­pseudorotaxane, namely, endo-benzyl and endo-alkyl, are formed by a stereoselectivity controlled by the endo-alkyl rule. Interestingly, by 1H NMR monitoring of the threading process between 8 + and 3, we revealed two calix[2]­pseudorotaxane isomers in which the calix-wheel adopts 1,2,3-alternate and cone conformations, which represent the kinetic and thermodynamic species, respectively. Finally, the synthesis of ammonium-based oriented calix[2]­rotaxane is here described.
ISSN:0022-3263
1520-6904
DOI:10.1021/acs.joc.7b01388