Green photochemistry: the use of microemulsions as green media in photooxygenation reactions

The use of 'green' microemulsions of ethyl acetate and water, using sodium dodecyl sulfate and alcoholic co-surfactants as a reaction medium, in photooxygenation reactions was investigated. This work looked at the optimisation of the microemulsion (the optimum ratio of components), an investigation of the effect of changing co-surfactant and optimisation of the reaction work-up for the synthesis of 5-hydroxy-1,4-naphthoquinone, Juglone. Isolated yields of 36–88% were achieved in just 4 h of irradiation. Microemulsions also allowed the usage of the sensitiser tetraphenylporphyrin (TPP) in a benign environment. The optimised procedure was furthermore applied to the synthesis of 5-amido-1,4-naphthoquinones, and moderate yields were achieved