Selective Synthesis of a [3]Rotaxane Consisting of Size-Complementary Components and Its Stepwise Deslippage

Abstract

An α-cyclodextrin-based size-complementary [3]rotaxane with an alkylene axle was selectively synthesized in one pot via an end-capping reaction with 2-bromophenyl isocyanate in water. Thermal degradation of the [3]rotaxane product yielded not only the original components but also the [2]rotaxane. Thermodynamic studies suggested a stepwise deslippage process.

Structural Analysis and Inclusion Mechanism of Native and Permethylated α‐Cyclodextrin‐Based Rotaxanes Containing Alkylene Axles

“…On the basis of the above results, we conclude that the directions or numbers of wheels in CD‐based rotaxanes containing short alkylene axles depend on 1) interactions between CDs, 2) the axle length, and 3) the affinity between the axle end and the tail face of the CD. Considering the importance of the directions of CDs for the deslipping behavior of CD‐based rotaxanes,, the present results provide useful information for the creation of new CD‐based rotaxane and polyrotaxane systems with predetermined numbers and directions of wheels. Furthermore, studies on the application of the newly synthesized PAcCD‐based rotaxanes, and other substituted CD‐based rotaxanes, are currently in progress.…”

“…Previously,w ed evelopedau rea end-cappingm ethod for synthesizing such CD-based rotaxanes consisting of as imple short alkylenea xle. [12] Thosee xperimental results suggested that the hydrogen bonds between native CDs would produce the head-to-head structure of ar otaxanew itha ne ven number of CDs. Hence, it was expected that OH-free CDs, such as permethylated CDs (PMeCD), would hardly restrict the structure of rotaxanec ompared with native CDs.…”

Direct Synthesis of an Oligomeric Series of Interlocked, Cyclodextrin‐Based [c2]Daisy Chains

“…Takata et al,, used 2‐bromo‐ and 3,5‐dimethyl‐phenylisocyanate as capping reagents to produce the [3]rotaxanes 5a and 5b , respectively (Figure ). While we reproduced the synthesis of 5b without difficulty, attempts to adapt that method using 4‐bromo‐2,6‐dimethylphenylisocyanate gave only very small amounts of the analogue 5c , as determined by HPLC and MALDI‐TOF mass spectrometry, even after extended reaction times and with large excesses of the isocyanate.…”

Assembly of [2]Rotaxanes in Water

“…The released water molecules participate in the hydrogen‐bonding network of the water bulk, which results in an enthalpy gain. Most known water‐soluble rotaxane systems that rely on the hydrophobic effect comprise cyclodextrin, pillar[ n ]arene, or cucurbit[ n ]uril as host molecules, and for some of these systems acidic media or organic co‐solvents are required , . Prominent examples of synthetically modifiable water‐soluble macrocycles are the quaternary ammonium‐functionalized dicationic spiro‐cyclophanes developed and extensively studied by Diederich and co‐workers , .…”