Arylacetic acids, when the carboxyl group is at a secondary or tertiary carbon, are decarboxylated in considerable yields on irradiation of their aqueous alkaline solutions with 254 nm light, while the corresponding free acids are not decarboxylated. Together with the simple decarboxylation reaction (type A), two other side reactions, oxidative decarboxylation (type B) and decarboxylative dimerization (type C), were observed for some compounds, particularly when >290 nm light was used. The observation of high-yield decarboxylation of angularly substituted phenanthridone derivatives suggests that the above photodecarboxylation reaction would be a useful synthetic tool, if the substrate is appropriately designed.
当羧基位于仲碳或叔碳上时,芳基
乙酸在用 254 纳米光照射其碱性
水溶液时会发生脱羧反应,产量相当可观,而相应的
游离酸则不会发生脱羧反应。除了简单的脱羧反应(A 型)外,在某些化合物中还观察到另外两种副反应,即氧化脱羧反应(B 型)和脱羧二聚反应(C 型),尤其是在使用波长大于 290 纳米的光源时。观察到角取代
菲啶酮衍
生物的高产脱羧反应表明,如果底物设计得当,上述光脱羧反应将是一种有用的合成工具。