Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States.
J Am Chem Soc. 2017 Mar 15;139(10):3868-3875. doi: 10.1021/jacs.7b00445. Epub 2017 Mar 1.
A cobalt-catalyzed method for the 1,1-diboration of terminal alkynes with bis(pinacolato)diboron (BPin) is described. The reaction proceeds efficiently at 23 °C with excellent 1,1-selectivity and broad functional group tolerance. With the unsymmetrical diboron reagent PinB-BDan (Dan = naphthalene-1,8-diaminato), stereoselective 1,1-diboration provided products with two boron substituents that exhibit differential reactivity. One example prepared by diboration of 1-octyne was crystallized, and its stereochemistry established by X-ray crystallography. The utility and versatility of the 1,1-diborylalkene products was demonstrated in a number of synthetic applications, including a concise synthesis of the epilepsy medication tiagabine. In addition, a synthesis of 1,1,1-triborylalkanes was accomplished through cobalt-catalyzed hydroboration of 1,1-diborylalkenes with HBPin. Deuterium-labeling and stoichiometric experiments support a mechanism involving selective insertion of an alkynylboronate to a Co-B bond of a cobalt boryl complex to form a vinylcobalt intermediate. The latter was isolated and characterized by NMR spectroscopy and X-ray crystallography. A competition experiment established that the reaction involves formation of free alkynylboronate and the two boryl substituents are not necessarily derived from the same diboron source.
一种钴催化的方法，用于将末端炔烃与双(频哪醇)二硼（BPin）进行 1,1-二硼化反应。该反应在 23°C 下高效进行，具有优异的 1,1-选择性和广泛的官能团容忍性。使用非对称二硼试剂 PinB-BDan（Dan = 萘-1,8-二氨基），立体选择性 1,1-二硼化提供了具有不同反应性的两个硼取代基的产物。通过 1-辛炔的二硼化反应制备的一个实例进行了结晶，并通过 X 射线晶体学确定了其立体化学。1,1-二硼基烯烃产物的实用性和多功能性在许多合成应用中得到了证明，包括癫痫药物噻加宾的简洁合成。此外，通过钴催化 1,1-二硼基烯烃与 HBPin 的氢硼化反应，实现了 1,1,1-三硼基烷烃的合成。氘标记和量热实验支持了一种机制，涉及炔基硼酸酯选择性插入钴硼化合物的 Co-B 键中，形成乙烯基钴中间体。后者通过 NMR 光谱和 X 射线晶体学进行了分离和表征。竞争实验确定该反应涉及游离炔基硼酸酯的形成，并且两个硼取代基不一定来自同一二硼源。
