Stabilization of Imines and Hemiaminals in Water by an Endo‐Functionalized Container Molecule

Stabilizing water‐sensitive reaction intermediates is challenging but desirable for guiding reactions to desired products in water. Herein, we report that labile imine and hemiaminal functional groups can be stabilized inside a synthetic container compound, a water‐soluble naphthotube. The naphthotube features a primary amine group anchored in a cavity with both hydrogen bonding sites and hydrophobic surfaces. Aldehydes in bulk aqueous solution are trapped in the cavity by the amine to form hemiaminals stabilized through hydrogen bonding and hydrophobic effects. Dehydration of the hemiaminal to the imine is favored by the release of water from the hydrophobic microenvironment. Both the hemiaminals and imines can be detected at room temperature by NMR spectroscopy and mass spectrometry. An amine‐functionalized naphthotube featuring a cavity with both hydrogen bonding sites and hydrophobic surfaces has been developed that traps aldehydes in bulk aqueous solution through the formation of hemiaminals. Dehydration of the hemiaminal to the imine is favored by the release of water from the hydrophobic microenvironment. Both the hemiaminals and imines could be detected by NMR spectroscopy and mass spectrometry at room temperature.