Dynamic effects are an important determinant of chemical reactivity and selectivity, but the deliberate manipulation of atomic motions during a chemical transformation is not straightforward. Here, we demonstrate that extrinsic force exerted upon cyclobutanes by stretching pendant polymer chains influences product selectivity through force-imparted nonstatistical dynamic effects on the stepwise ring-opening reaction. The high product stereoselectivity is quantified by carbon-13 labeling and shown to depend on external force, reactant stereochemistry, and intermediate stability. Computational modeling and simulations show that, besides altering energy barriers, the mechanical force activates reactive intramolecular motions nonstatistically, setting up “flyby trajectories” that advance directly to product without isomerization excursions. A mechanistic model incorporating nonstatistical dynamic effects accounts for isomer-dependent mechanochemical stereoselectivity.

动态效应是化学反应性和选择性的重要决定因素，但在化学转化过程中故意操纵原子运动并不简单。在这里，我们证明了通过拉伸聚合物侧链对环丁烷施加的外在力通过力赋予的非统计动态效应对逐步开环反应产生影响。高产物立体选择性通过碳 13 标记进行量化，并表明取决于外力、反应物立体化学和中间稳定性。计算建模和模拟表明，除了改变能垒外，机械力非统计地激活反应性分子内运动，建立“飞越轨迹”，直接进入产品而没有异构化偏移。