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Synfacts 2010(1): 0022-0022  
DOI: 10.1055/s-0029-1218465
Synthesis of Heterocycles
© Georg Thieme Verlag Stuttgart ˙ New York

FeCl3-Mediated Synthesis of Benzo[b]furans from α-Aryl Ketones

Contributor(s): Victor Snieckus, Cédric Schneider
Z. Liang, W. Hou, Y. Du*, Y. Zhang, Y. Pan, D. Mao, K. Zhao*
Tianjin University, P. R. of China
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Publication History

Publication Date:
21 December 2009 (online)

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Significance

Based on previous results from the same group (FeCl3-mediated intramolecular aromatic C-N bond coupling: K. Zhao and co-workers J. Org. Chem. 2008, 73, 2007), the synthesis of benzo[b]furans 2 via the FeCl3-mediated ring closure of the electron-rich α-aryl ketones 1 is reported. The presence of electron-donating groups in 1 is crucial for the success of the reaction. A SET mechanism is proposed in which the FeCl3 acts as a single electron oxidant. During optimization studies, a number of factors were revealed: the 4-MeO group is more critical to the success of the reaction than the 3-MeO group; the cyclization process was somewhat enhanced when R4 = Ph compared to R4 = Me; and when R³ = CN is replaced by other EWGs product 2 is obtained in moderate yields.