Masked Alkyne Equivalents for the Synthesis of Mechanically Interlocked Polyynes

Polyyne polyrotaxanes, encapsulated cyclocarbon catenanes and other fascinating mechanically interlocked carbonrich 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. Here we report the synthesis of a new bulky MAE based on a t-butylbicyclo[4.3.1]decatriene. This MAE was used to synthesize a polyyne [2]rotaxane and a maskedpolyyne [3]rotaxane by Cadiot-Chodkiewicz coupling. Glaser cyclooligomerization 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.