The excitation of carbonyl compounds by light to generate radical intermediates has historically been restricted to ketones and aldehydes; carboxylic acids have been overlooked because of high energy requirements and low quantum efficiency. A successful activation strategy would necessitate a bathochromic shift in the absorbance profile, an increase in triplet diradical lifetime, and ease of further functionalization. We present a single-flask transformation of carboxylic acids to acyl phosphonates that can access synthetically useful triplet diradicals under visible light or near-ultraviolet irradiation. The use of phosphorus circumvents unproductive Norrish type I processes, promoting selectivity that enables hydrogen-atom transfer reactivity. Use of this strategy promotes the efficient scaffold remodeling of carboxylic acids through various annulation, contraction, and expansion manifolds.

中文翻译：

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羧酸的光化学磷支架重塑


羰基化合物通过光激发生成自由基中间体历来仅限于酮和醛;由于高能量需求和低量子效率，羧酸一直被忽视。成功的激活策略需要吸光度曲线的变色变化，增加三重态二自由基的寿命，并易于进一步功能化。我们提出了一种将羧酸转化为酰基膦酸盐的单瓶转化，它可以在可见光或近紫外照射下获得合成有用的三联态二自由基。磷的使用规避了非生产性的 Norrish I 型过程，提高了选择性，使氢原子转移反应成为可能。使用该策略可促进羧酸通过各种环状、收缩和膨胀歧管进行有效的支架重塑。