Generation and Application of Radicals and Polyradicals

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This project established 1) a new and efficient radical generation method which is applicable to organic synthesis (investigation A), 2) a new route to trimethylenemethane diradical from [3] dendralene (investigation B), and 3) a methodology utilizing pyridinyl radicals as spin building blocks for high spin organic compounds (investigation C).In the investigation A,a very efficient and mild radical generation method was realized by utilizing Nacyloxyphthalimides which can be readily prepared from various carboxylic acid in high yields. The reaction proceeds in the presence of colored radical scavenger in aqueous solvent with visible light excitation at room temperature and the reaction is readily applied to reductive decarboxylation, decarboxylative phenylselenenylation, and decarboxylative phenyltellurenylation. The quantum yields of theses reactions are usually over unity and readily available right sources such as projector lamp, halogen lamp, and sunlight can be used. Since phenylselenenyl group is known to be converted to various functional groups, this method clearly widens the scope of synthetic methods starting from carboxylic acids.In the investigation B,a novel photochemical reaction of [3] dendralene derivative leading to trimethylenemethane diradical intermediate was found. The intermediate was successfully trapped by molecular oxygen or in the flash photolysis experiment.4,4'-(m-Phenylene) bis (1-menthyl-2,6-diphenylpyridinyl) diradical and its analogues were prepared and their spin-multiplicities in the ground states were investigated by means of ESR in the investigation C.