Department of Chemistry, Roy and Diana Vagelos Laboratories, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States.
Org Lett. 2017 Oct 20;19(20):5505-5508. doi: 10.1021/acs.orglett.7b02552. Epub 2017 Oct 12.
The first examples of asymmetric oxidative coupling of simple phenols and 2-hydroxycarbazoles are outlined. Generation of a more vanadium catalyst by ligand design and by addition of an exogenous Brønsted or Lewis acid was found to be key to coupling the more oxidatively resistant phenols. The resultant vanadium complex is both more Lewis acidic and more strongly oxidizing. Good to excellent levels of enantioselectivity could be obtained, and simple trituration readily provided the products with ≥95% ee.
概述了首例简单酚类和 2-羟基咔唑不对称氧化偶联的实例。通过配体设计和外加 Brønsted 或路易斯酸生成更具钒催化剂被发现是偶联更具氧化性的酚类的关键。所得的钒配合物具有更强的路易斯酸性和更强的氧化性。可以获得良好至优秀的对映选择性，并且简单的研磨很容易得到对映体过量值大于等于 95%的产物。
