Mechanical force-switchable aqueous organocatalysis

Control over the catalytic activity of artificial catalytic systems in aqueous media is of high interest for biomimetic artificial catalysts. The activity of catalytic systems can be controlled via introducing stimuli-responsive feature in the structure of the catalytic systems. However, temperature, pH or light have been predominantly used as stimulus. Aqueous catalytic system whose activity can be turned ‘ON/OFF’ employing mechanical force has not been demonstrated. Here we show how catalytic activity of an aqueous catalytic system can be switched ‘ON/OFF’ via the application/ceasing ultrasound stimulus. We demonstrate that the accessibility of imidazole, a catalyst moiety, can be modulated via the presence/absence of the ultrasound stimulus, resulting temporal control over the rate of ester hydrolysis reactions in aqueous buffer solution. This generic approach enables using a large range of organocatalysts for the preparation of molecules and/or materials in aqueous media for their application to material science, and in biomedical field. It is challenging to control the activity of artificial organocatalyst systems in aqueous media. Here, the organocatalytic activity of an aqueous catalytic system can be turned on or off for ester hydrolysis reactions using ultrasound stimulus.