The photo-Friedel-Crafts acylation of naphthoquinone in alternative “green” media and the photochemical generation of novel biaryl trifluoro phthalonitriles, their condensation to phthalocyanines and evaluation as singlet oxygen sensitisersud

摘要

The aim of this research was to investigate the photo-Friedel-Crafts acylation of napthoquinone with a variety of aldehydes using a Rayonet reactor. The long-term aim of this project was to apply this research to the synthesis of biologically active natural products such as alkannin and shikonin.udAs a 100% atom efficient, solar reaction, the photo-Friedel-Crafts acylation of naphthoquinone is understood to be a very environmentally friendly reaction. With this in mind, it was undertaken to improve the “green” nature of this reaction by replacing harmful traditional solvents such as benzene with more benign alternatives. Ionic liquids were chosen for this purpose, due to their low vapour pressure, recyclability, low flammability and customisable solubilising and catalytic properties, as well as the fact that they have been shown to stabilise reactions with radical intermediates. The reaction was also performed in microemulsions.udAs an extension of previous work done in DCU by Pratt et al. it was undertaken photochemically generate a series of biaryl trifluorophthalonitriles, and optimise the reaction conditions necessary for their synthesis. Once these novel phthalonitriles had been generated a method for condensing them to phthalocyanines was developed. The novel phthalocyanines generated using this method were then assessed as catalysts for photooxygenation reactions. It was hoped that the introduction of peripheral aryl groups would increase the solubility of the phthalocyanines as well as reducing aggregation.ud