Masked Alkyne Equivalents for the Synthesis of Mechanically Interlocked Polyynes**

Abstract

Polyyne polyrotaxanes, encapsulated cyclocarbon catenanes and other fascinating mechanically interlocked carbon‐rich architectures should become accessible if masked alkyne equivalents (MAEs) can be developed that are large enough to prevent unthreading of a macrocycle, and that can be cleanly unmasked under mild conditions. Herein, we report the synthesis of a new bulky MAE based on t‐butylbicyclo[4.3.1]decatriene. This MAE was used to synthesize a polyyne [2]rotaxane and a masked‐polyyne [3]rotaxane by Cadiot–Chodkiewicz coupling. Glaser cyclo‐oligomerization of the [2]rotaxane gave masked cyclocarbon catenanes. The unmasking behavior of the catenanes and rotaxanes was tested by photolysis at a range of UV wavelengths. Photochemical unmasking did not proceed cleanly enough to prepare extended encapsulated polyyne polyrotaxanes. We highlight the scope and challenges involved with this approach to interlocked carbon‐rich architectures.

Phenanthroline based rotaxanes: recent developments in syntheses and applications

“…Anderson's group reported an interesting strategy for the synthesis of a new class of polyyne based [2] and [3]rotaxanes bearing masked alkyne equivalents (MAE) as bulky stoppers which are large enough to prevent the dethreading of Scheme 24 Synthesis of [2]rotaxane with MAEs. 28 macrocyclic components (Scheme 24). 28 An alkyne, 74 and a bromoalkyne, 75 with MAE were prepared from indane.…”

“…28 macrocyclic components (Scheme 24). 28 An alkyne, 74 and a bromoalkyne, 75 with MAE were prepared from indane. Cadiot-Chodkiewicz coupling between 74 and 75 proceeded in presence of new macrocycle 76, CuI/K 2 CO 3 and furnished the [2] rotaxane, 77.…”

“…Anderson's group reported an interesting strategy for the synthesis of a new class of polyyne based [2] and [3]rotaxanes bearing masked alkyne equivalents (MAE) as bulky stoppers which are large enough to prevent the dethreading of macrocyclic components ( Scheme 24 ). 28 An alkyne, 74 and a bromoalkyne, 75 with MAE were prepared from indane. Cadiot–Chodkiewicz coupling between 74 and 75 proceeded in presence of new macrocycle 76, CuI/K 2 CO 3 and furnished the [2]rotaxane, 77.…”

Post‐Synthetic Macrocyclization of Rotaxane Building Blocks

“…The incorporation of porphyrins into interlocked molecules might be valuable for the control of their numerous properties, while alteration of a polyyne moiety by the presence of a surrounding macrocycle may be advantageously used. The same authors recently reported the copper‐mediated cyclo‐oligomerization under dilute conditions of the alkyne‐containing [2]rotaxane 13 into [3] and [4]catenanes 14 – 15 (Scheme 3c) [19] . In 13 , the t ‐butylbicyclo[4.3.1]decatrienes were utilized as masked alkyne equivalents (MAE) that are bulky enough to preserve the mechanical bond throughout the reaction.…”

“…The same authors recently reported the copper-mediated cyclo-oligomerization under dilute conditions of the alkyne-containing [2]rotaxane 13 into [3] and [4]catenanes 14-15 (Scheme 3c). [19] In 13, the tbutylbicyclo[4.3.1]decatrienes were utilized as masked alkyne equivalents (MAE) that are bulky enough to preserve the mechanical bond throughout the reaction. The absence of any template during the cyclization might explain the lower yields obtained in this case.…”