Generation and Application of Radicals and Polyradicals

该项目建立了1)适用于有机合成的新的有效的自由基生成方法(研究A)，2)从[3]树烯合成三亚甲基甲烷二自由基的新路线(研究B)，以及3)利用吡啶自由基作为高自旋有机化合物的自旋构筑块的方法(研究C)。在研究A中，利用容易从各种羧酸高产率制备的酰氧基邻苯二甲酰亚胺实现了一种非常高效和温和的自由基产生方法。该反应在有色自由基清除剂存在下，于室温下在可见光激发下进行，可用于还原脱羧化、脱羧基苯基亚硒化和脱羧基苯碲化反应。这些反应的量子产率通常超过单位，可以使用投影灯、卤素灯和太阳光等现成的合适光源。由于苯基亚硒基可以转化为各种官能团，该方法明显拓宽了从羧酸开始的合成方法的范围。在研究B中，发现了[3]树烯衍生物导致三亚甲基甲烷二自由基中间体的一种新的光化学反应。合成了4，4‘-(间苯基)双(1-薄荷基-2，6-二苯基吡啶基)二自由基及其类似物，并用电子自旋共振方法研究了它们在基态的自旋多重性。

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.