Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China.
Acc Chem Res. 2010 Oct 19;43(10):1342-51. doi: 10.1021/ar1000583.
The development of organometallic reagents remains one of the most important frontiers in synthetic chemistry. Commonly used organometallic reagents (such as RLi and RMgBr) are typically monometallic compounds, although they aggregate in many cases. When two carbon-metal bonds are in the same molecule in close proximity, however, these two carbon-metal moieties may exhibit novel reactivity. In this Account, we outline our work on new reactions and synthetic applications of the organo-dilithio reagents 1,4-dilithio-1,3-butadienes. The 1,4-dilithio-1,3-butadienes can be accessed readily in high efficiency with a wide variety of substitution patterns on the butadienyl skeleton. The configuration has been predicted and demonstrated to favor a double dilithium bridging structure in both solution and solid states. The two Li atoms are bridged by a butadiene moiety and are in close proximity. By taking advantage of this unique configuration, we have developed useful and interesting synthetic methodologies. Three types of reactions of 1,4-dilithio-1,3-butadienes, termed dilithio reagents here, have been developed and are discussed. An intramolecular reaction is introduced in the first section. The reaction is a result of the intracooperative effect among the two C-Li moieties, the butadienyl bridge, and the substituents. A useful transformation from silylated 1,4-dilithio-1,3-butadienes to α-lithio siloles is described. Second, we discuss an intermolecular reaction that results from the intercooperative effect of the two C-Li moieties toward substrates. As an example of the formation of functionalized cyclic dianions from the linear dianions of the dilithio reagents and organic substrates, we describe the isolation and structural characterization of a novel type of cyclic dianion; that is, fully substituted oxy-cyclopentadienyl dilithium formed via the reaction of dilithio reagents with CO. We also describe diverse reactions of dilithio reagents with nitriles to form substituted pyridines, tricyclic 1-bipyrrolines, and siloles, demonstrating the remarkable effect of substituents on the butadienyl skeleton. Third, we discuss transmetalation of dilithio reagents to generate other organo-dimetallic compounds. This section focuses on organo-dicopper compounds and their reactivity toward the synthesis of strained ring systems, such as semibullvalenes and twisted four-membered rings, with the metal-mediated C-C bond-forming approach. In addition to these three representative reactions, other useful applications are also briefly introduced. The dimetallic 1,4-dilithio-1,3-butadienes and their transmetalated derivatives provide unique synthetic organometallic reagents that are very different from monometallic reagents, both in terms of reactivity and synthetic application. These organo-dimetallic reagents provide access to interesting and useful compounds that are not available by other means. Moreover, given the possibilities afforded, the study of organo-dimetallic and organo-polymetallic compounds should yield further synthetic applications in the near future.
有机金属试剂的发展仍然是合成化学最重要的前沿领域之一。常用的有机金属试剂（如 RLi 和 RMgBr）通常是单金属化合物，尽管它们在许多情况下会聚集。然而，当两个碳-金属键在同一分子中紧密相邻时，这两个碳-金属部分可能表现出新颖的反应性。在本综述中，我们概述了我们在新型反应和有机二锂试剂 1,4-二锂-1,3-丁二烯的合成应用方面的工作。1,4-二锂-1,3-丁二烯可以通过各种取代模式在高效率下轻松获得。该结构已被预测并证明在溶液和固态中均有利于双锂桥接结构。两个 Li 原子通过丁二烯部分桥接，并且彼此靠近。通过利用这种独特的结构，我们开发了有用且有趣的合成方法。已经开发并讨论了 1,4-二锂-1,3-丁二烯的三种类型的反应，这里称为二锂试剂。在第一节中介绍了一种分子内反应。该反应是两个 C-Li 部分、丁二烯桥和取代基之间的协同作用的结果。描述了一种从硅化的 1,4-二锂-1,3-丁二烯到α-锂硅烷的有用转化。其次，我们讨论了一种由于两个 C-Li 部分对底物的协同作用而产生的分子间反应。作为由二锂试剂的线性二阴离子与有机底物形成官能化环状二阴离子的实例，我们描述了一种新型环状二阴离子的分离和结构特征；即，通过二锂试剂与 CO 的反应形成的完全取代的氧-环戊二烯基二锂。我们还描述了二锂试剂与腈的各种反应，以形成取代的吡啶、三环 1-联吡咯啉和硅烷，证明了丁二烯骨架上取代基的显著影响。第三，我们讨论了二锂试剂的transmetalation 以生成其他有机二金属化合物。本节重点介绍有机二铜化合物及其在通过金属介导的 C-C 键形成方法合成应变环系统（如半苯并环戊烯和扭曲的四元环）方面的反应性。除了这三种代表性反应外，还简要介绍了其他有用的应用。二价 1,4-二锂-1,3-丁二烯及其 transmetalated 衍生物提供了独特的合成有机金属试剂，它们在反应性和合成应用方面与单价试剂非常不同。这些有机二金属试剂可用于获得其他方法无法获得的有趣且有用的化合物。此外，鉴于所提供的可能性，研究有机二金属和有机多金属化合物应该在不久的将来产生进一步的合成应用。
