Premium
Efficient Synthesis of Benzofurans Utilizing [3,3]‐Sigmatropic Rearrangement Triggered by N ‐Trifluoroacetylation of Oxime Ethers: Short Synthesis of Natural 2‐Arylbenzofurans
Author(s) -
Takeda Norihiko,
Miyata Okiko,
Naito Takeaki
Publication year - 2007
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200601001
Subject(s) - chemistry , sigmatropic reaction , oxime , reagent , acylation , total synthesis , ether , yield (engineering) , beckmann rearrangement , organic chemistry , combinatorial chemistry , catalysis , materials science , metallurgy
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 oracyclic 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. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)