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

---

see article for more reactions

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.

see article for more examples

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