烯烃是各种材料和生物活性分子中的基本官能团;然而,对其立体定义合成的有效发散策略是困难的。在这方面,已经开发了许多合成方法来构建具有区域选择性和立体选择性的碳-碳键,使立体定义的烯烃的可预测和有效的合成。事实上,一种用于访问具有挑战性的立体定义的烯烃分子框架的有吸引力的替代方法可能涉及强键的顺序选择性激活和交叉偶联,而不是常规的C-C键形成。在这项研究中,我们介绍了一系列程序化的位点和立体选择性策略,这些策略利用了易于获得的多金属类烯烃(即多硼化烯烃)的通用反应性,通过串联交叉偶联反应,由有机金属Rh络合物催化产生复杂的分子支架。通过合并选择性C-B和远程C-H键官能化,我们实现了多官能C(sp2)亲核中间体的原位生成。这些物质可以通过与各种基于C的亲电试剂的选择性偶联反应进一步修饰,使用容易获得的起始聚硼化烯烃,能够形成C(sp2)-C(sp3)键,以产生甚至更复杂的分子结构。机理和计算研究通过1,4-Rh迁移过程提供了对立体选择性和C-H活化的起源的见解。
Alkenes are fundamental functional groups which feature in various materials and bioactive molecules; however, efficient divergent strategies for their stereodefined synthesis are difficult. In this regard, numerous synthetic methodologies have been developed to construct carbon-carbon bonds with regio- and stereoselectivity, enabling the predictable and efficient synthesis of stereodefined alkenes. In fact, an appealing alternative approach for accessing challenging stereodefined alkenes molecular frameworks could involve the sequential selective activation and cross-coupling of strong bonds instead of conventional C-C bond formation. In this study, we introduce a series of programmed site- and stereoselective strategies that capitalizes on the versatile reactivity of readily accessible polymetalloid alkenes (i.e. polyborylated alkenes), through a tandem cross-coupling reaction, which is catalyzed by an organometallic Rh-complex to produce complex molecular scaffolds. By merging selective C-B and remote C-H bond functionalization, we achieve the in-situ generation of polyfunctional C(sp2)-nucleophilic intermediates. These species can be further modified by selective coupling reactions with various C-based electrophiles, enabling the formation of C(sp2)-C(sp3) bond for the generation of even more complex molecular architectures using the readily available starting polyborylated-alkenes. Mechanistic and computational studies have provided insight into the origins of the stereoselectivities and C-H activation via a 1,4-Rh migration process.