Abstract

Due to their ease of preparation, stability, and diverse reactivity, N-hydroxyphthalimide (NHPI) esters have found many applications as radical precursors. Mechanistically, NHPI esters undergo a reductive decarboxylative fragmentation to provide a substrate radical capable of engaging in diverse transformations. Their reduction via single-electron transfer (SET) can occur under thermal, photochemical, or electrochemical conditions and can be influenced by a number of factors, including the nature of the electron donor, the use of Brønsted and Lewis acids, and the possibility of forming charge-transfer complexes. Such versatility creates many opportunities to influence the reaction conditions, providing a number of parameters with which to control reactivity. In this perspective, we provide an overview of the different mechanisms for radical reactions involving NHPI esters, with an emphasis on recent applications in radical additions, cyclizations and decarboxylative cross-coupling reactions. Within these reaction classes, we discuss the utility of the NHPI esters, with an eye towards their continued development in complexity-generating transformations.

Beilstein J. Org. Chem. 2024, 20, 346–378. doi:10.3762/bjoc.20.35

摘要

由于其易于制备、稳定性和多样化的反应性，N-羟基邻苯二甲酰亚胺 (NHPI) 酯已作为自由基前体得到许多应用。从机理上讲，NHPI 酯经历还原脱羧裂解，提供能够参与多种转化的底物自由基。它们通过单电子转移 (SET) 的还原可以在热、光化学或电化学条件下发生，并且可能受到许多因素的影响，包括电子供体的性质、布朗斯特酸和路易斯酸的使用以及形成电荷转移复合物。这种多功能性创造了许多影响反应条件的机会，提供了许多控制反应性的参数。从这个角度来看，我们概述了涉及 NHPI 酯的自由基反应的不同机制，重点介绍了最近在自由基加成、环化和脱羧交叉偶联反应中的应用。在这些反应类别中，我们讨论了 NHPI 酯的实用性，着眼于它们在复杂性生成转化方面的持续发展。

贝尔斯坦 J. 组织。化学。 2024, 20, 346–378。doi:10.3762/bjoc.20.35