Preparation of Pillar[5]arene‐Based [2]Rotaxanes from Acyl Chlorides and Amines

Abstract

Pillar [5]arene-based [2]rotaxanes have been prepared from the reactions of diacyl chloride reagents with various amine stoppers. The yields of the [2]rotaxanes are sensitive to the reaction conditions (solvent and stoichiometry) as well as to structural and electronic factors. In particular, the nature of the starting amine reagent has a dramatic influence on the yields of [2]rotaxanes; thus, the reaction outcome is not simply related to the binding constant of the diacyl chloride reagent with the pillar[5]arene. Indeed, the differences in the

Diversity Oriented Preparation of Pillar[5]arene‐Containing [2]Rotaxanes by a Stopper Exchange Strategy

“…The reaction was performed in CHCl 3 , a solvent that does not compete with diol 1 for the formation of inclusion complexes with pillar[5]arene 2 . To further favor the formation of pseudorotaxane intermediates, the reaction was performed at the highest possible concentration (0.49 M for 2 ) and at the lowest possible temperature (−15 °C) . Under optimized conditions, compound 3 was obtained in 62 % yield.…”

Mechanochemical Solvent‐Free Conditions for the Synthesis of Pillar[5]arene‐Containing [2]Rotaxanes

“…Inclusion complex [ 1 ⊂ 2 ] was obtained by mixing an equimolar mixture of 1 and 2 in CHCl 3 . The association constant for the 1:1 complex is rather weak (log K a = 1.86 in CDCl 3 at 25 °C) . In order to favor the assembly of pseudo‐rotaxane intermediate [ 1 ⊂ 2 ], the mixture of 1 and 2 was prepared in a minimum amount of solvent and cooled to –15 °C.…”

“…a pseudorotaxane, is often limited by low binding constants. This is for example the case for the preparation of [2]rotaxanes from the reaction of amine stoppers with the inclusion complex resulting from the association of dodecanedioyl dichloride ( 2 ) and pillar[5]arene 1 (Scheme ) . The yields in rotaxanes are particularly sensitive to the nature of the starting amine reagents as it modulates the affinity of the mono‐amide intermediate for macrocycle 1 .…”

A Fullerene‐Substituted Pillar[5]arene for the Construction of a Photoactive Rotaxane

“…This value is rather low and photophysical studies in dilute solutions to demonstrate excited state interactions between the fullerene acceptor and the porphyrin donor in supramolecular ensemble [ 7 ⊂ 6a ] cannot be carried out under optimal conditions. However, the K A value is still sufficiently high to prepare a rotaxane from [ 7 ⊂ 6a ] by installing a stopper on the terminal hydroxyl group of subunit 7 ( Scheme ) . In the resulting rotaxane, both the fullerene and the porphyrin subunits will be connected through mechanical bonds and dissociation will not be possible any longer.…”

“…However, the K A value is still sufficiently high to prepare a rotaxane from [7⊂6a] by installing a stopper on the terminal hydroxyl group of subunit 7 (Scheme 3). [33] [34] In the resulting rotaxane, both the fullerene and the porphyrin subunits will be connected through mechanical bonds and dissociation will not be possible any longer. Rotaxane 9 was obtained by reaction of a mixture of 6a and 7 with acyl chloride 8.…”