Highly Regioselective Palladium-Catalyzed Direct Arylation of Oxazole at C-2 or C-5 with Aryl Bromides, Chlorides, and Triflates
Neil A. Strotman*, Harry R. Chobanian*, Yan Guo, Jiafang He and Jonathan E. Wilson
*Department of Process Chemistry and Department of Medicinal Chemistry, Merck Research Laboratories, Merck & Co., Inc., P.O. Box 2000, Rahway, New Jersey 07065, Email: neil_strotmanmerck.com, harry_chobanianmerck.com
N. A. Strotman, H. R. Chobanian, Y. Guo, J. He, J. E. Wilson, Org. Lett., 2010, 12, 3578-3581.
DOI: 10.1021/ol1011778 (free Supporting Information)
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Complementary methods for direct arylation of oxazoles with high regioselectivity at both C-5 and C-2 have been developed for a wide range of aryl and heteroaryl bromides, chlorides, iodides, and triflates. Using task-specific phosphine ligands, palladium-catalyzed C-5 arylation of oxazoles is preferred in polar solvents, whereas C-2 arylation is preferred in nonpolar solvents.
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