期刊
TETRAHEDRON LETTERS
卷 51, 期 6, 页码 955-958出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.tetlet.2009.12.047
关键词
Benzofuran; Benzoquinone; Stilbene oxide; Dehydrative cycloaddition; Lewis acid
资金
- Ministry of Education, Culture, Sports, Science, and Technology, Japan
We report a BF(3)-mediated novel dehydrative cycloaddition reaction of benzoquinones with stilbene oxides to afford 2,3-diaryl-5-hydroxybenzofurans and 2,3-diai-yl-5-hydroxydihydrobenzofurans in good combined yields. No change in the products or the yield is observed when using diphenylacetaldehyde and cis-stilbene oxide instead of trans-stilbene oxides. When stilbene oxide is reacted with hydroquinone instead of the corresponding benzoquinone under the same conditions, dihydrobenzofuran is isolated in high yield. On the basis of these results, we propose the following possible reaction mechanism: stilbene oxide is converted to a phenonium ion (the key intermediate), which undergoes nucleophilic attack by benzoquinone or the simultaneously generated hydroquinone and subsequent dehydrative intramolecular cyclization to afford benzofuran or dihydrobenzofuran, respectively. (C) 2009 Elsevier Ltd. All rights reserved.
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