Promoting Difficult Carbon-Carbon Couplings: Which Ligand Does Best?

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• 作者：Estefaní ; a Gioria ; Dr. Juan del Pozo ; Dr. Jes&uacute ; s M. Martí ; nez-Ilarduya and Prof. Dr. Pablo Espinet
• 刊名：Angewandte Chemie International Edition
• 出版年：2016
• 出版时间：October 10, 2016
• 年：2016
• 卷：55
• 期：42
• 页码：13276-13280
• 全文大小：875K
• ISSN：1521-3773

文摘

A Pd complex, cis-[Pd(C₆F₅)₂(THF)₂] (1), is proposed as a useful touchstone for direct and simple experimental measurement of the relative ability of ancillary ligands to induce C−C coupling. Interestingly, 1 is also a good alternative to other precatalysts used to produce Pd⁰L. Complex 1 ranks the coupling ability of some popular ligands in the order P^tBu₃>o-TolPEWO-F≈tBuXPhos>P(C₆F₅)₃≈PhPEWO-F>P(o-Tol)₃≈THF≈tBuBrettPhos≫Xantphos≈PhPEWO-H≫PPh₃ according to their initial coupling rates, whereas their efficiency, depending on competitive hydrolysis, is ranked tBuXPhos≈P^tBu₃≈o-TolPEWO-F>PhPEWO-F>P(C₆F₅)₃≫tBuBrettPhos>THF≈P(o-Tol)₃>Xantphos>PhPEWO-H≫PPh₃. This “meter” also detects some other possible virtues or complications of ligands such as tBuXPhos or tBuBrettPhos.