Diazo compounds and N-tosylhydrazones: novel cross-coupling partners in transition-metal-catalyzed reactions.
Diazo compounds and N-tosylhydrazones: novel cross-coupling partners in transition-metal-catalyzed reactions.
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DOI：
10.1021/ar300101k
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发表时间：
2013-02
影响因子：
18.3
通讯作者：
Q. Xiao;Yan Zhang;J. Wang
中科院分区：
文献类型：
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作者：
Q. Xiao;Yan Zhang;J. Wang
过渡金属催化的卡宾转化和交叉偶联代表了有机金属化学和有机合成中的两种主要反应类型。然而，长期以来，这两个重要领域各自发展，基本上没有重叠或融合。因此，出现了一个有趣的问题：交叉耦合和金属卡宾转化能否合并到一个反应循环中？这种组合可以促进新型碳-碳键形成方法的开发。尽管这个概念在大约10年前就被首次探索，但最近该领域取得了快速发展。钯催化剂可用于将重氮化合物与多种有机卤化物偶联。在氧化偶联条件下，重氮化合物也可以与芳基硼酸和末端炔烃发生反应。这两个偶联反应均形成碳-碳双键。作为这些催化过程中的关键步骤，Pd 卡宾迁移插入在合并 Pd 中间体的基本步骤中发挥着至关重要的作用，导致新型碳-碳键的形成。由于重氮底物可以在碱存在下由N-甲苯磺酰腙原位生成，因此N-甲苯磺酰腙可以用作反应伙伴，使得这种类型的交叉偶联反应在有机合成中实用。 N-甲苯磺酰腙很容易衍生自相应的醛或酮。 Pd 催化的 N-甲苯磺酰腙交叉偶联被认为是经典夏皮罗反应的补充反应，用于将羰基官能团转化为碳-碳双键。它还可以作为钯催化羰基化合物交叉偶联的替代方法，这通常是通过三氟甲磺酸酯实现的。卡宾形成和交叉偶联在单个催化循环中的组合并不限于 Pd 催化反应。最近对 Cu、Rh、Ni 和 Co 催化的与重氮化合物或 N-甲苯磺酰腙的交叉偶联反应的研究表明，这些转化也适用于其他过渡金属，证明了重氮化合物作为过渡金属催化偶联反应中新的交叉偶联伙伴的普遍性。
Transition-metal-catalyzed carbene transformations and cross-couplings represent two major reaction types in organometallic chemistry and organic synthesis. However, for a long period of time, these two important areas have evolved separately, with essentially no overlap or integration. Thus, an intriguing question has emerged: can cross-coupling and metal carbene transformations be merged into a single reaction cycle? Such a combination could facilitate the development of novel carbon-carbon bond-forming methodologies. Although this concept was first explored about 10 years ago, rapid developments inthis area have been achieved recently. Palladium catalysts can be used to couple diazo compounds with a wide variety of organic halides. Under oxidative coupling conditions, diazo compounds can also react with arylboronic acids and terminal alkynes. Both of these coupling reactions form carbon-carbon double bonds. As the key step in these catalytic processes, Pd carbene migratory insertion plays a vital role in merging the elementary steps of Pd intermediates, leading to novel carbon-carbon bond formations. Because the diazo substrates can be generated in situ from N-tosylhydrazones in the presence of base, the N-tosylhydrazones can be used as reaction partners, making this type of cross-coupling reaction practical in organic synthesis. N-Tosylhydrazones are easily derived from the corresponding aldehydes or ketones. The Pd-catalyzed cross-coupling of N-tosylhydrazones is considered a complementary reaction to the classic Shapiro reaction for converting carbonyl functionalities into carbon-carbon double bonds. It can also serve as an alternative approach for the Pd-catalyzed cross-coupling of carbonyl compounds, which is usually achieved via triflates. The combination of carbene formation and cross-coupling in a single catalytic cycle is not limited to Pd-catalyzed reactions. Recent studies of Cu-, Rh-, Ni-, and Co-catalyzed cross-coupling reactions with diazo compounds or N-tosylhydrazones show that these transformations also work with other transition metals, demonstrating the generality of the diazo compounds as new cross-coupling partners in transition-metal-catalyzed coupling reactions.