Organic Letters
Letter
Scheme 3. Synthesis in Flow and Product Transformation
AUTHOR INFORMATION
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Corresponding Author
ORCID
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
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Financial support of this research from MOST (No.
2016YFA0204100), NSFC (No.s, 21672178, 21402164), and
the “Thousand Youth Talents Plan”.
efficiently cleaved and replaced with a synthetically useful
trimethylsilylmethyl group in the presence of a Ni catalyst
(Scheme 3).14d
A possible mechanism for the electrolytic C−H oxygenation
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of amide 1 was illustrated in Scheme 4. The electrolytic
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Scheme 4. Proposed Mechanism
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reaction begins with the anodic oxidation of the electron-rich
methoxylated phenyl ring in 1 to form the radical cation A. The
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methoxy group, which is sterically less hindered than the ortho
position and also where the SOMO is mainly located,7b,15
furnishes the cyclohexadienyl radical B after deprotonation.
Rearomatization of B via electron and proton elimination
furnishes the final product 2.
In summary, we have developed an electrochemical method
that can be used to prepare a variety of 4H-1,3-benzoxazines via
the aromatic C−H functionalization of N-benzylamides. The
reaction showed a broad substrate scope and satisfactory
regioselectivity despite the susceptibility of the benzoxazine
products to overoxidation. We also demonstrated that a
microflow electrolysis cell could be employed to achieve easy
reaction scale-up and to reduce the use of supporting
electrolyte.
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ASSOCIATED CONTENT
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* Supporting Information
The Supporting Information is available free of charge on the
Experimental procedure and characterization data (PDF)
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