Rotaxanes and Catenanes by Click Chemistry

Abstract

Copper(I)-catalyzed Huisgen 1,3-dipolar cycloaddition between terminal alkynes and azides -also known as the copper (Cu)-catalyzed Azide-Alkyne Cycloaddition (CuAAC) -has been used in the syntheses of molecular compounds with diverse structures and functions, owing to its functional group tolerance, facile execution, and mild reaction conditions under which it can be promoted. Recently, rotaxanes of four different structural types, as well as donor/acceptor catenanes, have been prepared using CuAAC, attesting to its tolerance to supramolecular interactions as well. In one instance of a rotaxane synthesis, the catalytic role of copper has been combined successfully with its previously documented ability to preorganize rotaxane precursors, i.e., form pseudorotaxanes. The crystal structure of a donor/acceptor catenane formed using the CuAAC reaction indicates that any secondary [p ··· p] interactions between the 1,2,3-triazole ring and the bipyridinium p-acceptor are certainly not destabilizing. Finally, the preparation of robust rotaxane and catenane molecular monolayers onto metal and semiconductor surfaces is premeditated based upon recent advances in the use of the Huisgen reaction for surface functionalization.

The application of CuAAC ‘click’ chemistry to catenane and rotaxane synthesis

“…The metal-free [3]rotaxane could be obtained, however, by replacing iron(II) as the template with cobalt(III). 23 Oxidation of Co(III) into labile Co(II) made the rotaxane decomplexation quick and efficient (Na 3 HEDTA, DMSO) affording the metalfree [3]rotaxane 21 in quantitative yield. The dethreading process 36 of metal-free 21 was followed by 1 H NMR and its half-life was determined to be one week in CH 2 Cl 2 at room temperature.…”

“…Addition of pyridine as a competitive ligand-in order to remove the metal catalyst from the sequestrating rotaxane-enabled the catalyst to turn over, giving 82% (incorrectly reported as 38% in ref. 23) of rotaxane 10a using only 20 mol% Cu(I). This marked the first time that only catalytic quantities of a template were necessary to synthesise a mechanically interlocked architecture.…”

“…23 To date the CuAAC reaction has been used in catenane and rotaxane synthesis in four different ways: to build hard-toobtain structures by linking together small fragments into bigger and more complex structures or covalently capturing threaded supramolecular complexes, the modification of pre-existing structures (including decoration and postsynthetic functionalisation), the combination of both of these approaches where the CuAAC is used to link building blocks and as a functionalisation tool, and finally the use of preformed triazole rings as ligands for the assembly of, and to play a role in controlling the dynamics of, mechanically interlocked architectures.…”

Click Chemistry Under Microwave or Ultrasound Irradiation

“…As such, it is clear that MW-and US-promoted CuAAC will act as R X + NaN 3 + R' US, [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] …”

“…Other works highlight the developments in carbohydrate-based drug discovery and glycobiology [27] in proteomics probes [28] and in a niche sector such as the preparation of rotaxanes and catenane [29].…”