Accelerating a Mechanically Driven <i>anti</i>-Woodward–Hoffmann Ring Opening with a Polymer Lever Arm Effect

Abstract

Mechanical forces have previously been used to drive reactions along pathways that violate the orbital symmetry effects captured in the Woodward–Hoffmann rules. Here, we show that a polymer “lever arm effect” can provide a mechanical advantage in accelerating the symmetry forbidden disrotatory ring opening of benzocyclobutene (BCB). Addition of an α-<i>E</i>-alkene to the BCB mechanophore drops the force required to induce reactions on the ∼0.1 s time scale of single-molecule force spectroscopy experiments from 1370 to 920 pN