Microwave activation and solvent-free phase transfer catalysis for the synthesis of new benzylidene cineole derivatives as potential UV sunscreens

Abstract

Microwave activation coupled with solvent-free phase transfer catalysis (PTC), as a green chemistry procedure, was applied to the synthesis of new benzylidene cineole derivatives as potential UVA filters. Considerable improvements over classical procedures are put into evidence when using KOH + K₂CO₃ as the base and TBAB as the phase transfer agent. Comparison with conventional heating in strictly the same conditions as under microwave revealed an important specific non-thermal microwave effect. Preliminary studies to evaluate the photochemical behaviour of these new derivatives were carried out.