Here we report the mechanochemical reactivity of the highly strained pentacyclic hydrocarbon cubane. The mechanical reactivity of cubane is explored for three regioisomers with 12- 13- and 14-substituted pulling attachments. Whereas all compounds can be activated thermally mechanical activation is observed via pulsed ultrasonication of cubane-containing polymers only when force is applied via 12-attachment. The single observed product of the force-coupled reaction is a thermally inaccessible syn-tricyclooctadiene in contrast to cyclooctatetraene (observed thermally) or a pair of cyclobutadienes that would result from sequential cyclobutane scission. We further quantify the mechano-chemical reactivity of cubane by single molecule force spectroscopy and force-coupled rate constants for ring opening reach ~33 s-1 at a force of ~1.55 nN lower than forces of 1.8-2.0 nN that are typical of conventional cyclobutanes.
