Reaction Optimization, Scalability, and Mechanistic Insight on the Catalytic Enantioselective Desymmetrization of 1,1‐Diborylalkanes via Suzuki–Miyaura Cross‐Coupling
作者:Ho‐Yan Sun、Koji Kubota、Dennis G. Hall
DOI:10.1002/chem.201406680
日期:2015.12.21
aryl groups and the amino group on the ligand must be achieved. While the base has been known to facilitate transmetallation in cross‐coupling reactions, mechanistic studies on this desymmetrization process reveal that the base, in the presence of KHF2, likely plays an additional role in the hydrolysis of the pinacol boronates to the corresponding boronic acids. Through an in depth optimization of the
通过立体选择性的Pd催化的Suzuki-Miyaura交叉偶联,对1,1-二硼烷基烷烃进行对映选择性去对称化的方法已得到彻底优化。发现最有效的配体是α,α,α,α-四芳基-1,3-二氧戊环-4,5-二甲醇(TADDOL)衍生的亚磷酰胺。结果表明,为了获得高的选择性,必须在芳基的空间和配体上的氨基的空间之间达到适当的平衡。尽管已知该碱可促进交叉偶联反应中的金属转移,但对该去对称化过程的机理研究表明,该碱在存在KHF 2的情况下,可能在频哪醇硼酸酯水解成相应的硼酸中起另外的作用。通过对手性配体的深入优化和机理研究,有可能获得多种芳基溴的ee值超过90%,并开发出可靠的可扩展工艺(最多1克1,1-二硼烷基烷烃底物)。