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Structural Determinants of Alkyne Reactivity in Copper-Catalyzed Azide-Alkyne Cycloadditions
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Molecules 2017, 22(1), 89;

Stepwise, Protecting Group Free Synthesis of [4]Rotaxanes

Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK
School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
Author to whom correspondence should be addressed.
Academic Editor: Roman Dembinski
Received: 21 November 2016 / Revised: 22 December 2016 / Accepted: 25 December 2016 / Published: 9 January 2017
(This article belongs to the Special Issue Recent Advances in CuAAC Click Chemistry)
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Despite significant advances in the last three decades towards high yielding syntheses of rotaxanes, the preparation of systems constructed from more than two components remains a challenge. Herein we build upon our previous report of an active template copper-catalyzed azide-alkyne cycloaddition (CuAAC) rotaxane synthesis with a diyne in which, following the formation of the first mechanical bond, the steric bulk of the macrocycle tempers the reactivity of the second alkyne unit. We have now extended this approach to the use of 1,3,5-triethynylbenzene in order to successively prepare [2]-, [3]- and [4]rotaxanes without the need for protecting group chemistry. Whilst the first two iterations proceeded in good yield, the steric shielding that affords this selectivity also significantly reduces the efficacy of the active template (AT)-CuAAC reaction of the third alkyne towards the preparation of [4]rotaxanes, resulting in severely diminished yields. View Full-Text
Keywords: rotaxane; mechanically interlocked; copper-catalyzed azide-alkyne cycloaddition; CuAAC; active template rotaxane; mechanically interlocked; copper-catalyzed azide-alkyne cycloaddition; CuAAC; active template

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Lewis, J.E.M.; Winn, J.; Goldup, S.M. Stepwise, Protecting Group Free Synthesis of [4]Rotaxanes. Molecules 2017, 22, 89.

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