ORGANIC
LETTERS
2011
Vol. 13, No. 11
2970–2973
Preparation of Functional Benzofurans,
Benzothiophenes, and Indoles Using
Ester, Thioester, and Amide via
Intramolecular Wittig Reactions
Siang-en Syu, Yu-Ting Lee, Yeong-Jiunn Jang, and Wenwei Lin*
Department of Chemistry, National Taiwan Normal University, 88, Section 4,
Tingchow Road, Taipei 11677, Taiwan, ROC
Received April 22, 2011
ABSTRACT
Preparation of new types of highly functional benzofurans, benzothiophenes, and indoles is realized via intramolecular Wittig reactions with the
corresponding ester, thioester, and amide functionalities. The key intermediates, phosphorus ylides, presumably result from the addition of Bu3P
toward aldehydes followed by acylation and deprotonation. Synthesis of functional benzofurans directly starting from salicylic aldehyde
derivatives with acid chlorides in a one-step procedure is also developed.
Benzofurans 1,1 benzothiophenes 2,1bÀd,2 and indoles
31,3 are important classes of heterocycles present in
pharmaceuticals and many natural products. Different
types of substitution patterns in these heterocycles provide
new opportunities for drug discoveries and other applica-
tions in material science. However, in order to prepare new
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r
10.1021/ol201062r
Published on Web 05/12/2011
2011 American Chemical Society