Generation and Application of Radicals and Polyradicals

本项目建立了1)一种适用于有机合成的高效自由基生成新方法（研究a）； 2)一条由[3]树突烯生成三甲基乙烷双自由基的新途径（研究B）； 3)一种利用吡啶基自由基作为高自旋有机化合物的自旋构建单元的方法（研究C）。在研究A中，利用由各种羧酸制备的酰氧苯酞酰亚胺，实现了一种高效、温和的自由基生成方法。在室温可见光激发下，在有色自由基清除剂存在的水溶液中进行反应，该反应易于应用于还原性脱羧、脱羧性苯硒化和脱羧性苯碲化。这些反应的量子产率通常超过一单位，并且可以使用投影灯、卤素灯和阳光等合适的光源。由于已知苯硒基可以转化为各种官能团，因此该方法显然拓宽了从羧酸开始的合成方法的范围。在研究B中，发现了一种新的树突烯衍生物生成三甲基乙烷二自由基中间体的光化学反应。该中间体通过分子氧或闪光光解实验成功捕获。制备了4,4′-（间苯基）双（1-甲基-2,6-二苯基吡啶基）双自由基及其类似物，并用ESR研究了它们在基态上的自旋多重性。

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.