Stepwise Functionalization of a Pillararene‐Containing Rotaxane with Pentafluorophenyl Ester Stoppers

• Published in: Chemistry : a European journal Vol. 30; no. 4
• Main Authors: Becharguia, Nihed, Wasielewski, Emeric, Abidi, Rym, Nierengarten, Iwona, Jean‐François Nierengarten
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01-01-2024
• Subjects: Acylation; Carbonyl compounds; Carbonyl groups; Carbonyls; Chemistry; Conformation; Organic solvents; Reagents; Rotaxanes; Shafts (machine elements); Solvents
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202303501

Detailed investigations into 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 to 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 that are particularly difficult to prepare under statistical conditions. Finally, detailed conformation 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, whereas solvophobic effects play a major role in polar solvents.Dedicated to Prof. Maurizio Prato on the occasion of his 70th birthday.