Lighting the way to carbon borylation Boron substituents provide versatile reactivity, and their utility has been emerging in pharmaceutical contexts. Fawcett et al. show that visible light can induce replacement of carboxylic acid groups with boronate esters, which will ease their introduction into a wide variety of compounds. Once the acids are activated with phthalimide substituents, they can react with catecholborane dimers under illumination in amide solvents, with no need for catalysts or other additives. The reaction appears to proceed by radical chain propagation after photoinitiation. Science, this issue p. 283 Light facilitates the replacement of carboxylic acids with boron esters in the absence of metal catalysts. The conversion of widely available carboxylic acids into versatile boronic esters would be highly enabling for synthesis. We found that this transformation can be effected by illuminating the N-hydroxyphthalimide ester derivative of the carboxylic acid under visible light at room temperature in the presence of the diboron reagent bis(catecholato)diboron. A simple workup allows isolation of the pinacol boronic ester. Experimental evidence suggests that boryl radical intermediates are involved in the process. The methodology is illustrated by the transformation of primary, secondary, and tertiary alkyl carboxylic acids as well as a diverse range of natural-product carboxylic acids, thereby demonstrating its broad utility and functional group tolerance.

中文翻译：

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羧酸的光诱导脱羧硼酰化

照亮碳硼化的道路 硼取代基提供了多种反应性，并且它们的效用已经出现在制药领域。福西特等人。表明可见光可以诱导硼酸酯取代羧酸基团，这将有助于将它们引入各种化合物中。一旦酸被邻苯二甲酰亚胺取代基活化，它们就可以在酰胺溶剂中在光照下与儿茶酚硼烷二聚体反应，无需催化剂或其他添加剂。该反应似乎通过光引发后的自由基链增长进行。科学，这个问题 p。283 Light 有助于在没有金属催化剂的情况下用硼酯替代羧酸。将广泛可用的羧酸转化为多功能硼酸酯将非常有助于合成。我们发现，在二硼试剂双（儿茶酚）二硼存在下，在室温下，在可见光下照射羧酸的 N-羟基邻苯二甲酰亚胺酯衍生物，可以实现这种转化。简单的后处理可以分离频哪醇硼酸酯。实验证据表明，硼基自由基中间体参与了该过程。该方法通过伯、仲和叔烷基羧酸以及各种天然产物羧酸的转化来说明，从而证明其广泛的实用性和官能团耐受性。