Microwave-assisted solvent-free synthesis of fluorescent naphthalimide dyes

• We prepare 4-substituted-1,8-naphthalimide dyes in the presence of KF/Al2O3.
• We accelerate the synthesis of fluorescent dyes via using microwave irradiation.
• We use different amines, alcohols and thiols for the functionalization of dyes.

A series of fluorescent naphthalimide dyes were synthesized via aromatic nucleophilic substitution reaction of 4-bromo-N-alkylnaphthalimides with amines, alkoxides and thiols under microwave irradiation. In this procedure an efficient method for C–N, C–O and C–S bond formation via applying appropriate nucleophiles in the presence of KF/Al2O3 under solvent-free conditions is described. Adducts are produced in good to excellent yields and relatively in short times. The optical properties of three dyes as representative derivatives were examined by UV absorption and steady state fluorescence spectroscopy in solvents with different polarity.

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