Chemistry. 2023 Nov 20:e202303501. doi: 10.1002/chem.202303501. Online ahead of print.
ABSTRACT
Detailed investigations on the stepwise bis-functionalization of a pillar[5]arene-containing rotaxane building block have been carried out. Upon a first stopper exchange, the pillar[5]arene moiety of the mono-acylated product is preferentially located close to its reactive pentafluorophenyl ester stopper, thus limiting the accessibility of the reactive carbonyl group by the nucleophilic reagents. Selective mono-functionalization is thus very efficient. Introduction of a second stopper is then possible to generate dissymmetrical rotaxanes with different amide stoppers. Moreover, when dethreading is possible upon the second acylation, the pillar[5]arene plays the role of a protecting group allowing the synthesis of dissymmetrical axles particularly difficult to prepare under statistical conditions. Finally, detailed conformational analysis of the rotaxanes revealed that the position of the pillar[5]arene moiety on its axle subunit is mainly governed by polar interactions in nonpolar organic solvents while solvophobic effects are playing a major role in polar solvents.
PMID:37983752 | DOI:10.1002/chem.202303501
