Nakao Yoshiaki
Department of Material Chemistry, Graduate School of Engineering, Kyoto University Katsura, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
Chem Rev. 2021 Jan 13;121(1):327-344. doi: 10.1021/acs.chemrev.0c00301. Epub 2020 Oct 13.
Nitriles are ubiquitous versatile building blocks in organic synthesis. Common reactions of nitriles include the transformation of cyano groups into carbonyl and amine moieties. The functionalization of nitriles can also be accomplished at the alpha-position of alkanenitriles and at the ortho-position of cyanoarenes. On the other hand, the C-CN bond of nitriles has rarely been recognized as a valuable reaction site due to its thermodynamic robustness. Although it has been known for a long time in organometallic chemistry that C-CN bonds can be cleaved by transition-metal complexes, this elemental reaction had not been used in catalytic synthetic transformations of nitriles until two decades ago. This review surveys the progress of metal-catalyzed reactions of nitriles via C-CN bond activation. After introducing several different modes to activate C-CN bonds by various transition metals, catalytic reactions are categorized mainly into two parts: (i) reactions with CN as a leaving group and (ii) reactions with nitriles as a source of CN groups. Cross-coupling-type transformations with a cyano leaving group, cyanation reactions using nitriles as a nontoxic cyano source, and novel synthetic reactions such as carbocyanation are highlighted together with useful demonstrations of their utility in organic synthesis.
腈是有机合成中普遍存在的多功能结构单元。腈的常见反应包括将氰基转化为羰基和胺基部分。腈的官能团化也可以在烷腈的α位和氰基芳烃的邻位实现。另一方面，由于腈的C-CN键具有热力学稳定性，很少被认为是一个有价值的反应位点。尽管在有机金属化学中人们早就知道C-CN键可以被过渡金属配合物裂解，但直到二十年前，这种基本反应才被用于腈的催化合成转化。本文综述了通过C-CN键活化实现的金属催化腈反应的进展。在介绍了几种通过各种过渡金属活化C-CN键的不同模式后，催化反应主要分为两部分：(i) 以CN作为离去基团的反应和 (ii) 以腈作为CN基团来源的反应。重点介绍了带有氰基离去基团的交叉偶联型转化反应、使用腈作为无毒氰基来源的氰化反应以及碳氰化等新型合成反应，并展示了它们在有机合成中的实用性。
