钯催化卤代烷烃参与的自由基型转化反应

Palladium-Catalyzed Radical-Type Transformations of Alkyl Halides

钯催化的交叉偶联反应经历了数十年的发展,已经成为一种重要的有机合成手段.相比于芳基和烯基卤代物,烷基卤代物参与的偶联反应具有诸多挑战,例如烷基卤代物和钯催化剂发生氧化加成较为困难,之后形成的烷基钯物种也面临易于发生β-H消除和质子化等副反应的挑战.近年来,有机化学家们大力发展了涉及单电子转移的新型钯催化体系,实现了烷基卤代物参与的一系列自由基型偶联反应,弥补了传统双电子转化模式的不足.本文以参与反应的底物类型为序,综述了近年来钯催化卤代烷烃的自由基型转化反应新进展.

Palladium-catalyzed cross-coupling reactions have been developed for decades as useful methods in organic synthesis. Compared to aryl and alkenyl halides, alkyl halides are more challenging to be applied in cross-coupling reactions. This mainly arises from the difficulty in oxidative addition of alkyl halides to palladium catalyst, sluggish reductive elimination and competitive side reactions, such as β-H elimination and protonation, of the resulting alkylpalladium intermediates. These challenges have partly been overcome with the significant development of novel palladium catalysis involving single election transfer. A variety of cross couplings of alkyl halides have been developed. In this review the recent palladium-catalyzed radical alkylation using alkyl halides with the order of different types of coupling partners is summarized.