Some of the first synthetically useful metal-catalyzed reactions reported involved first-row transition metals and the complexity of their reactivity was evident even 60 years ago, but it is only recently that homogeneous catalysis with first-row transition metals has become the focus of academic research and industrial synthesis efforts. On the other hand, the development of second- and third-row catalysis rapidly developed in the 1960s–1990s, perhaps in part because their basic mechanistic steps, once defined, could be used, like Legos, to construct a myriad of catalytic cycles. These catalytic reactions revolutionized how organic molecules were made in the pharmaceutical industry. In the process, catalysis went from a niche class of chemistry, viewed as unreliable except for hydrogenation, to being an invaluable strategy, ubiquitous across organic synthesis. A convergence of two large trends, one from academia and one from industry, created the perfect climate for the growth of first-row catalysis. First, the increasing industrial reliance on precious metal catalysis led to concerns about their limited global supply, the security of those supplies, and their environmental impacts. Second, the advances in mechanistic understanding of second- and third-row transition-metal catalysts set the stage for academic researchers to tackle the complexities of first-row metals. At first, inspired by the chemistry of second- and third-row transition-metal catalysts, researchers developed approaches to avoid the 1-electron chemistry of the first row. Ultimately, however, it was realized that first-row metals, by their ability to access both 2-electron and 1-electron steps, enabled a wide array of new reactions that are impossible with second- and third-row metals. In this exciting Special Issue, leaders in the field of nonprecious metal catalysis highlight how mechanistic insights transformed the perceived challenges of first-row transition-metal catalysts into strengths. Access to both two-electron and one-electron steps increases the complexity of controlling selectivity in catalytic reactions but offers new avenues for control. The Account by Elizabeth Jarvo discusses how, depending upon the ligand bound to the catalyst, nickel catalysts can control stereochemistry stereospecifically (via S_N2-type reactivity) and stereoselectively (via radical pathways). Instead of stereochemistry, Sophie Rousseaux relates how switching between 1-electron and 2-electron pathways leads to different outcomes of reactions and the design of approaches to C(sp³)–O bond functionalization that takes advantage of 1-electron chemistry. Sarah Reisman’s Account demonstrates how improvements in the understanding of ligand effects and electrophile activation can lead to improvements in the scope and selectivity of enantioselective nickel-catalyzed cross-coupling and cross-electrophile coupling reactions. The variety of oxidation states accessible to first-row transition metals presents challenges when only one has the desired reactivity. Shannon Stahl presents an Account of a way to control the oxidation state through the assistance of a “redox-buffer” that keeps a copper catalyst on-cycle. Controlling the catalyst oxidation state requires understanding what oxidation states give the desired reactivity. This is easier said than done with first-row metals, but Tianning Diao discusses their efforts to shed light on the fundamentals of different nickel oxidation states and how they are controlled by the ligand sphere. In both cases, the improved understanding has been utilized to develop new chemistry that addresses synthetic needs in complex, pharmaceutically relevant targets. With increased understanding of the mechanism complexities has come an appreciation of how this complexity can be tamed to enable replacement of precious metals and can be leveraged to unlock new reactivity. Naoto Chatani discusses how mechanistic understanding was used to convert older stoichiometric nickel C–H activation reactivity into modern catalytic C–H functionalization chemistry. In a complementary story, Ryan Shenvi discusses how the single-electron chemistry of first-row metals is particularly well suited to the challenges of C(sp³)–C(sp³) bond formation and complex molecule synthesis. Ming Joo Koh relates how a variety of first-row transition metals (Ni, Fe, Ti, and Mn) can unlock new reactivity from familiar reagents to address long-standing challenges in alkene difunctionalization and sugar chemistry. Guoyin Yin details how the kinetically fast but thermodynamically unfavorable β-hydride elimination with late first-row metals such as nickel can be utilized for novel 1,n-difunctionalizations of alkenes, where one of the new bonds is made at a remote C–H site. The weaker ligand field of first-row transition metals means that ligand exchange and loss is faster than with heavier transition metals. In the Account by Shaolin Zhu, this challenge is converted to an advantage by using a ligand relay approach to 1,n-alkene difunctionalization with chain-walking. There are also practical considerations that need to be solved for making first-row catalysts useful. A perennial challenge for first-row transition metals is seemingly simple: what precatalyst to use? This is a major challenge in nickel catalysis because accessing the right oxidation state is critical, but the important low-oxidation-state nickel complexes are usually very oxygen-sensitive. Keary Engle relates efforts to make nickel chemistry more accessible by creating reactive nickel(0) precatalysts that are bench-stable. The electron-poor ligands studied also have exciting reactivity for challenging transformations. Another question is how to drive the reaction. While thermal reactions are historically the norm for second- and third-row metals, Martins Oderinde discusses how the flexibility of nickel catalysis extends to a variety of modalities: thermal, photochemical, and electrochemical. We hope readers enjoy reading these Accounts as much as we did and are inspired to try out first-row transition metals in their own research. This article has not yet been cited by other publications.

中文翻译：

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曾经和未来的催化剂：第一行过渡金属催化的挑战如何发展成为优势


一些最早报道的合成有用的金属催化反应涉及第一行过渡金属，其反应性的复杂性在 60 年前就已经很明显了，但直到最近，第一行过渡金属的均相催化才成为学术界的焦点研究和工业合成工作。另一方面，第二排和第三排催化的发展在 20 世纪 60 年代至 90 年代迅速发展，部分原因可能是它们的基本机械步骤一旦定义，就可以像乐高积木一样用来构建无数的催化循环。这些催化反应彻底改变了制药工业中有机分子的制造方式。在此过程中，催化从一种小众化学（除了氢化之外被认为不可靠）转变为一种宝贵的策略，在有机合成中无处不在。学术界和工业界两大趋势的融合，为一线催化的发展创造了完美的环境。首先，工业对贵金属催化的依赖日益增加，引发了人们对其有限的全球供应、这些供应的安全性及其环境影响的担忧。其次，对第二和第三行过渡金属催化剂的机理理解的进步为学术研究人员解决第一行金属的复杂性奠定了基础。起初，受到第二行和第三行过渡金属催化剂化学的启发，研究人员开发了避免第一行单电子化学的方法。然而，最终人们认识到，第一行金属由于能够同时进行 2 电子和 1 电子步骤，从而能够实现第二和第三行金属不可能发生的一系列新反应。 在这一令人兴奋的特刊中，非贵金属催化领域的领导者强调了机械见解如何将第一行过渡金属催化剂的感知挑战转化为优势。获得双电子和单电子步骤增加了控制催化反应选择性的复杂性，但提供了新的控制途径。 Elizabeth Jarvo的叙述讨论了镍催化剂如何根据与催化剂结合的配体，立体定向（通过 S _N 2 型反应性）和立体选择性（通过自由基途径）控制立体化学。 Sophie Rousseau没有讲述立体化学，而是讲述了 1 电子和 2 电子途径之间的切换如何导致不同的反应结果，以及利用 1 电子化学的 C(sp ³ )–O 键功能化方法的设计。 Sarah Reisman 的账户展示了对配体效应和亲电试剂活化的理解的提高如何能够改善对映选择性镍催化交叉偶联和交叉亲电试剂偶联反应的范围和选择性。当只有一种过渡金属具有所需的反应性时，第一行过渡金属可达到的各种氧化态提出了挑战。 Shannon Stahl提出了一种通过“氧化还原缓冲液”的帮助来控制氧化态的方法，该缓冲液使铜催化剂保持循环。控制催化剂氧化态需要了解什么氧化态可提供所需的反应性。 对于第一行金属来说，说起来容易做起来难，但刁天宁讨论了他们为阐明不同镍氧化态的基本原理以及它们如何受配体球控制而做出的努力。在这两种情况下，加深的理解都被用来开发新的化学物质，以满足复杂的、药物相关目标的合成需求。随着对机制复杂性的了解不断加深，人们开始认识到如何驾驭这种复杂性以实现贵金属的替代，并如何利用这种复杂性来释放新的反应性。 Naoto Chatani讨论了如何利用机理理解将旧的化学计量镍 C-H 活化反应性转化为现代催化 C-H 功能化化学。在补充故事中， Ryan Shenvi讨论了第一行金属的单电子化学如何特别适合应对 C(sp ³ )–C(sp ³ ) 键形成和复杂分子合成的挑战。 Ming Joo Koh讲述了各种第一行过渡金属（Ni、Fe、Ti 和 Mn）如何从熟悉的试剂中释放出新的反应性，以解决烯烃双官能化和糖化学中长期存在的挑战。尹国银详细介绍了如何利用镍等后第一行金属进行动力学快速但热力学不利的 β-氢化物消除来实现烯烃的新型 1, n-双官能化，其中一个新键是在远程 C–H 上形成的地点。第一行过渡金属的配体场较弱，这意味着配体交换和损失比较重的过渡金属更快。 在Shaolin Zhu的叙述中，通过使用配体中继方法通过链行走实现 1, n-烯烃双官能化，这一挑战转化为优势。为了使第一行催化剂发挥作用，还需要解决一些实际问题。第一行过渡金属面临的长期挑战看似简单：使用什么预催化剂？这是镍催化中的一个主要挑战，因为获得正确的氧化态至关重要，但重要的低氧化态镍络合物通常对氧非常敏感。 Keary Engle介绍了通过创建实验室稳定的反应性镍 (0) 预催化剂来使镍化学更容易实现的努力。研究的贫电子配体对于具有挑战性的转化也具有令人兴奋的反应性。另一个问题是如何驱动反应。虽然热反应历来是第二排和第三排金属的常态，但Martins Oderinde讨论了镍催化的灵活性如何扩展到各种模式：热反应、光化学反应和电化学反应。我们希望读者像我们一样喜欢阅读这些报道，并受到启发在自己的研究中尝试第一行过渡金属。这篇文章尚未被其他出版物引用。