Cu-Catalyzed Synthesis of Benzoxazole with Phenol and Cyclic Oxime
Zheng-Hai Wang1, Dong-Hui Wang1,2
1Laboratory of Synthetic and Self-Assembly Chemistry for Organic Functional Molecules, University of Chinese Academy of Sciences, Shanghai Institute of Organic Chemistry, CAS, 345 Lingling Road, Shanghai 200032, China.
Abstract:
A Cu-catalyzed straightforward synthesis of benzoxazoles from free phenols and cyclic oxime esters is reported. The mild reaction conditions tolerate various electron-withdrawing and electron-donating functional groups on both substrates, affording benzoxazoles in moderate to good yields. With this protocol, large-scale syntheses of Ezutromid and Flunoxaprofe in one or two steps are demonstrated. A catalytic mechanism, which includes Cu-catalyzed amination via inner-sphere electron transfer and consequent annulation, is proposed.
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