期刊
EUROPEAN JOURNAL OF ORGANIC CHEMISTRY
卷 2007, 期 9, 页码 1491-1509出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/ejoc.200601001
关键词
benzofuran; sigmatropic rearrangement; total synthesis; trifluoroacetic anhydride; trifluoroacetyl triflate
A new synthetic method for the preparation of benzofurans has been developed. The key step of this method is the [3,3]-sigmatropic rearrangement of N-trifluoroacetyl-ene-hydroxylamines, which was triggered by acylation of oxime ethers. TFAA has been proved to be the best reagent to induce [3,3]sigmatropic rearrangement for the synthesis of cyclic or acyclic dihydrobenzofurans. On the other hand, the TFAT-DMAP system is found to be the most effective for constructing various benzofurans. Synthetic utility of this reaction is demonstrated by the short synthesis of natural benzofurans without protection of the hydroxy group. The synthesis of Stemofuran A was accomplished via condensation of ketones with aryloxyamine and subsequent reaction with TFAT-DMAP in a four-step synthesis with 72% overall yield. Similarly, Eupomatenoid 6 and Coumestan were synthesized through the reaction of oxime ether with TFAT-DMAP. ((c) Wiley-VCH Verlag GmbH & Co.
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