本文描述了银催化末端炔烃 Z 选择性加氢烷基化的详细机理研究。考虑到已建立的炔烃Z选择性加氢烷基化机制范例,我们探索了一种基于炔烃自由基碳金属化的机制。实验结果为反对最初提出的自由基机理提供了强有力的证据,并促使我们提出一种基于硼酸酯形成和1,2-金属化物转移的炔烃Z选择性加氢烷基化的新机制。新机制为反应中观察到的优异 Z 选择性提供了理论依据。一系列化学计量实验探讨了所提出的基本步骤的可行性,并揭示了银催化剂在中间体的原脱硼中的附加作用。最后,一系列动力学测量、KIE 实验和竞争实验使我们能够确定周转限制步骤和催化剂的静止状态。我们相信本研究结果将对炔烃相关转化的进一步探索和发展有所帮助。
Synthesis of Isomerically Pure (<i>Z</i>)-Alkenes from Terminal Alkynes and Terminal Alkenes: Silver-Catalyzed Hydroalkylation of Alkynes
作者:Mitchell T. Lee、Madison B. Goodstein、Gojko Lalic
DOI:10.1021/jacs.9b09336
日期:2019.10.30
molecules and often are used as intermediates in organic synthesis. Many alkenes exist in two stereoisomeric forms (E and Z), which have different structures and different properties. The selective formation of the two isomers is an important synthetic goal that has long inspired the development of new synthetic methods. However, the efficient synthesis of diastereopure, thermodynamically less stable, Z-alkenes
Stereospecific Ni-Catalyzed Cross-Coupling of Potassium Alkenyltrifluoroborates with Alkyl Halides
作者:Gary A. Molander、O. Andreea Argintaru
DOI:10.1021/ol500408a
日期:2014.4.4
A general method for the alkenylation of alkyl electrophiles using nearly stoichiometric amounts of the air- and moisture-stable potassium organotrifluoroborates has been developed. Various functional groups were tolerated on both the nucleophilic and electrophilic partner. Reactions of highly substituted E- and Z-alkenyltrifluoroborates, as well as vinyl- and propenyltrifluoroborates, were successful, and no loss of stereochemistry or regiochemistry was observed.