有机电合成已被广泛用作常规氧化还原反应方法的环保替代方法,因为它利用电流作为无痕迹的氧化还原剂而不是化学氧化还原剂。采用氧化还原催化剂的间接电解受到了极大的关注,因为与直接电解相比,它提供了各种优势。通过间接电解,可以避免电子转移的过电势,本质上更温和,因此可以实现宽的官能团耐受性。此外,化学选择性,区域选择性,和立体选择性可以通过间接电解中使用的氧化还原催化剂来调节。此外,可以通过防止在电极表面上形成聚合物膜来避免电极钝化。常见的氧化还原催化剂包括N-氧基自由基,高价碘物种,卤化物,胺,苯醌(如DDQ和四氯苯醌),过渡金属。近年来,在使用过渡金属作为氧化还原催化剂进行包括C-H官能化在内的反应类别的间接有机电合成领域取得了重大进展,自由基环化,和芳基卤化物的交叉偶联-每种都是由于过渡金属的不同反应性和可达到的氧化态。尽管有各种有关有机电合成的评论,缺乏专注于使用过渡金属的间接电解领域的最新研究进展的文章,这是这次审查的动力。
Organic electrosynthesis has been widely used as an environmentally conscious alternative to conventional methods for redox reactions because it utilizes electric current as a traceless redox agent instead of chemical redox agents. Indirect electrolysis employing a redox catalyst has received tremendous attention, since it provides various advantages compared to direct electrolysis. With indirect electrolysis, overpotential of electron transfer can be avoided, which is inherently milder, thus wide functional group tolerance can be achieved. Additionally, chemoselectivity, regioselectivity, and stereoselectivity can be tuned by the redox catalysts used in indirect electrolysis. Furthermore, electrode passivation can be avoided by preventing the formation of polymer films on the electrode surface. Common redox catalysts include N-oxyl radicals, hypervalent iodine species, halides, amines, benzoquinones (such as DDQ and tetrachlorobenzoquinone), and transition metals. In recent years, great progress has been made in the field of indirect organic electrosynthesis using transition metals as redox catalysts for reaction classes including C-H functionalization, radical cyclization, and cross-coupling of aryl halides-each owing to the diverse reactivity and accessible oxidation states of transition metals. Although various reviews of organic electrosynthesis are available, there is a lack of articles that focus on recent research progress in the area of indirect electrolysis using transition metals, which is the impetus for this review.