State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China.
State Key Laboratory of Natural Medicines (SKLNM) and Department of Medicinal Chemistry, School of Pharmacy, China Pharmaceutical University, Nanjing 210009, China.
Acc Chem Res. 2022 Dec 6;55(23):3519-3536. doi: 10.1021/acs.accounts.2c00628. Epub 2022 Nov 9.
Transition metal hydride catalyzed functionalization of remote and proximal olefins has many advantages over conventional cross-coupling reactions. It avoids the separate, prior generation of stoichiometric amounts of organometallic reagents and the use of preformed organometallic reagents, which are sometimes hard to access and may compromise functional group compatibility. The migratory insertion of metal hydride complexes generated into readily available alkene starting materials, the hydrometalation process, provides an attractive and straightforward route to alkyl metal intermediates, which can undergo a variety of sequential cross-coupling reactions. In particular, with the synergistic combination of chain-walking and cross-coupling chemistry of nickel, NiH-catalyzed functionalization of remote and proximal olefins has undergone particularly intense development in the past few years. This Account aims to chronicle the progress made in this arena in terms of activation modes, diverse functionalizations, and chemo-, regio-, and enantioselectivity.We first provide a brief introduction to the general reaction mechanisms. Taking remote hydroarylation as an example, the four oxidation states of Ni have allowed us to develop two different reaction strategies to form the final product: a Ni(I)-H/X-Ni(II)-H platform that relies on stoichiometric reductants and a Ni(I/II/III) cycle and a redox-neutral functional group or FG-Ni(II)-H platform that reacts with an alkene substrate and forms the migratory products via a Ni(0/II) pathway. We also demonstrate that diverse functionalization, including general C-C bond-forming reactions and the more challenging C-N/C-S bond-forming reactions could be realized. Moreover, the employment of appropriate chiral ligands has allowed us to successfully realize the corresponding asymmetric hydrofunctionalization reactions of olefins, including hydroalkylation, hydroarylation, hydroalkenylation, hydroalkynylation, and hydroamination. Interestingly, the enantio-determining step could be enantioselective hydronickelation, selective oxidative addition, or selective reductive elimination. To realize more challenging asymmetric migratory hydrofunctionalization, we have developed a general ligand relay catalytic strategy with a combination of two simple ligands, the first for chain-walking and the second for asymmetric coupling. This novel strategy avoids the design of a single, possibly structurally complex chiral ligand to promote both steps of chain-walking and asymmetric coupling. In addition, the success of multicomponent hydrofunctionalization provides a convenient approach to gain simple access to complex molecules. Finally, alkyl halides could be used as olefin precursors to undergo a variety of reductive migratory cross-electrophile coupling reactions. Applications of these remote hydrofunctionalization reactions are also discussed. We hope this Account will inspire future development in the field to overcome key challenges, including conceptually new catalytic strategies, development of high-performance systems with enhanced reactivity and selectivity, cutting-edge catalyst design, and further mechanistic studies.
过渡金属氢化物催化的远程和近端烯烃功能化具有许多优于传统交叉偶联反应的优点。它避免了分开、预先生成化学计量的有机金属试剂和使用预形成的有机金属试剂,这些试剂有时难以获得并且可能影响官能团的兼容性。金属氢化物配合物的迁移插入生成 到易得的烯烃起始原料中,即氢金属化过程,为烷基金属中间体提供了一种有吸引力和直接的途径,这些中间体可以进行各种连续的交叉偶联反应。特别是,在镍的链行走和交叉偶联化学的协同组合作用下,NiH 催化的远程和近端烯烃功能化在过去几年中得到了特别深入的发展。本账户旨在根据活化模式、各种功能化以及化学、区域和对映选择性来记录该领域的进展。我们首先简要介绍一般反应机制。以远程氢芳基化为例,Ni 的四种氧化态使我们能够开发两种不同的反应策略来形成最终产物:一种依赖于化学计量还原剂的 Ni(I)-H/X-Ni(II)-H 平台和一种 Ni(I/II/III)循环和氧化还原中性官能团或 FG-Ni(II)-H 平台,该平台与烯烃底物反应并通过 Ni(0/II)途径形成迁移产物。我们还表明,可以实现各种功能化,包括一般的 C-C 键形成反应和更具挑战性的 C-N/C-S 键形成反应。此外,适当的手性配体的使用使我们能够成功地实现烯烃的相应不对称氢官能化反应,包括氢烷基化、氢芳基化、氢烯丙基化、氢炔基化和氢氨化。有趣的是,对映决定步骤可以是对映选择性氢镍化、选择性氧化加成或选择性还原消除。为了实现更具挑战性的不对称迁移氢官能化,我们开发了一种通用的配体接力催化策略,该策略结合了两种简单的配体,一种用于链行走,另一种用于不对称偶联。这种新策略避免了设计单一的、可能结构复杂的手性配体来促进链行走和不对称偶联的两步反应。此外,多组分氢官能化的成功提供了一种方便的方法来获得复杂分子。最后,烷基卤化物可用作烯烃前体,以进行各种还原迁移交叉亲电偶联反应。还讨论了这些远程氢官能化反应的应用。我们希望本账户将激发该领域未来的发展,以克服关键挑战,包括概念上的新催化策略、开发具有增强的反应性和选择性的高性能系统、前沿催化剂设计以及进一步的机理研究。
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