A novel coumarin Schiff base fluorescent probe ethyl 7-hydroxycoumarin-3-carboxylate-8-formaldehyde benzoyl hydrazone （EBH） has been designed and synthesized which shows solvent dependent dual sensing, viz., recognition of Ca^2＋ in DMF-H20 （9 ： 1, V/V） solution based on C=N isomerization, photoinduced electron transfer （PET） inhibition and chelation-enhanced fluorescence （CHEF） mechanism as well as detection of Zn^2＋ in HzO-CH3OH （9 ： 1, V/V） solution by excited-state intramolecular proton transfer （ESIPT） and CHEF processes. The structure of the probe EBH has been confirmed by single-crystal X-ray diffraction analysis. Meanwhile, the probe was also used to image intracellular Zn^2＋ ions in MCF-7 cells with a good performance.
Since the early studies of Mannich, Mannich reaction has become an important tool for the synthesis of new compounds. Mannich bases can be either directly employed or used as intermediates. In this work, the one-carbon unit transfer reaction of tetrahydrofolate coenzyme was initiated. 1,3-Dimethylimidazolidine as a new tetrahydrofolate coenzyme model at formaldehyde oxidation level was used to react with ketone having active hydrogen atoms and amine to give the corresponding Mannich base in good yield by a covert Mannich reaction. A novel method for biomimetic synthesis of various Mannich bases is provided.
