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2.3.2.1.7.2 Synthesis of Benzoxazoles by Intramolecular Copper-Catalyzed Oxygenation of Arene C(sp)—H Bonds

DOI: 10.1055/sos-SD-208-00284

Inamoto, K.Science of Synthesis: Cross Coupling and Heck-Type Reactions, (20132421.

Substituted benzoxazoles 49 are efficiently prepared from benzanilides 48 through a C—H bond functionalization/intramolecular C—O bond-forming cyclization process in the presence of copper(II) trifluoromethanesulfonate as a catalyst and dioxygen or air as the sole oxidant (Table 5).[‌25‌,‌26‌] Interestingly, the reactions of substrates possessing a halogen atom or a methoxy group as a meta-substituent occur at the less hindered site, whereas benzanilides with other meta-substituents, such as pyrrolidinone, carbamate, acetyl, benzoyl, or formyl groups, cyclize at the more hindered site. The latter regioselectivity can be explained in terms of the formation of doubly coordinated intermediate 50 (Scheme 22).

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