The Role of Dethreading Process in Pseudorotaxanes and Rotaxanes towards Advanced Applications: Recent Examples

Abstract

Rotaxanes are a type of mechanically interlocked molecules (MIMs), constituted by at least a thread surrounded by a wheel, which are widely employed in the research field of artificial molecular machines. Although applications retaining the integrity of the mechanical bond are usually reported, the dethreading of the components can be crucial to develop some advanced applications. Thus, different dethreading strategies have been reported, and advanced applications which require such a process have turned out to be suitable approaches towards machine‐like operation. This review article covers recent examples of applications of pseudorotaxanes and rotaxanes in which dethreading processes have a key role to accomplish the desired function.

Sacrificial Mechanical Bond is as Effective as a Sacrificial Covalent Bond in Increasing Cross-Linked Polymer Toughness

“…The kinetics and mechanisms of rotaxane dethreading that occurs without concomitant rearrangement of covalent bonds has been little studied apart from qualitative observations about the importance of the size of the stopper group 24,46 (blue in Figure 2). Consequently, we used DFT calculations to identify the stoppers (Figure 3) with potentially exploitable optimizations of the transition states, and hence calculations of activation free energies, and required us to optimize the geometries at a less computationally demanding level of BLYP/6-31G(d).…”

Synthesis of ‘Impossible’ Rotaxanes

“…rotaxanes, [13] together with post-synthetic modifications of the structure avoiding the dethreading process, [14] turns out to be one key strategy for obtaining 'impossible' rotaxanes.…”

Stereoselective synthesis of β-lactams: recent examples

“…The macrocycle is the activating element but also the element that dictates the diastereoselectivity, which leads to the obtention of the trans -adducts as the only products. In order to obtain the noninterlocked β-lactams, a dethreading process is carried out, 71 thus allowing the obtention of the target bioactive heterocycles.…”

“…The macrocycle is the activating element but also the element that dictates the diastereoselectivity, which leads to the obtention of the trans-adducts as the only products. In order to obtain the noninterlocked β-lactams, a dethreading process is carried out, 71 thus allowing the obtention of the target bioactive heterocycles. But in addition to the regio-and diastereoselections, this research group carried out a rational design incorporating stereocenters, either positioned in the linear counterpart 72 or in the cyclic one, 73 to induce enantioselection in the process.…”