On‐off Pulsed Ultrasound Promote Asymmetric Noncovalent Organocatalysis “on Water”: An Investigation in Michael Addition and Diels‐Alder Reactions

Abstract Pulsed ultrasonic irradiation with on‐off modulation remarkably enhances asymmetric noncovalent organocatalysis “on water”, specifically for Michael addition and Diels‐Alder reactions. This approach effectively addresses challenges associated with solid reactant dispersion encountered in “on‐water” reactions and mitigates overheating issues caused by continuous ultrasound exposure, thereby significantly augmenting reaction rates and stereoselectivities.