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Efficient Synthesis of Benzofurans Utilizing [3,3]-Sigmatropic Rearrangement Triggered by N-Trifluoroacetylation of Oxime Ethers: Short Synthesis of Natural 2-Arylbenzofurans

Norihiko Takeda, Okiko Miyata, Takeaki Naito*

*Kobe Pharmaceutical University, Motoyamakita, Higashinada, Kobe 658-8558, Japan, Email: taknaitokobepharma-u.ac.jp

N. Takeda, O. Miyata, T. Naito, Eur. J. Org. Chem., 2007, 1491-1509.

DOI: 10.1002/ejoc.200601001


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Abstract

TFAA induces a [3,3]-sigmatropic rearrangement of N-trifluoroacetyl-ene-hydroxylamines for the synthesis of dihydrobenzofurans, whereas reactions with TFAT-DMAP gives benzofurans. The synthetic utility is demonstrated by the short synthesis of natural benzofurans without protection of the hydroxy group.


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proposed mechanism



Thermal cyclization of N-trifluoracetyl enehydrazines under mild conditions: A novel entry into the Fischer indole synthesis

O. Miyata, Y. Kimura, K. Muroya, H. Hiramatsu, T. Naito, Tetrahedron Lett., 1999, 40, 3601-3604.


Key Words

Benzofurans


ID: J24-Y2007-2280