Asymmetric Oxidative Coupling of Phenols and Hydroxycarbazoles
Houng Kang1, Young Eun Lee1, Peddiahgari Vasu Govardhana Reddy1
1Department of Chemistry, Roy and Diana Vagelos Laboratories, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States.
Abstract:
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.
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