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Paper | Regular issue | Vol 38, No. 3, 1994, pp.641-658
Published online, 1st January, 1970
DOI: 10.3987/COM-93-6623
Fused Furan Construction via an Intramolecular [3+2] Cycloaddition Reaction: Syntheses of 4H-Cyclohepta- and 4H-Cyclopenta[b]furans

Kozo Shishido,* Koji Umimoto, and Masayuki Shibuya

*Institute for Medicinal Resources, University of Tokushima, 1-78 Sho-machi, Tokushima 770-8505, Japan

Abstract

General and efficient syntheses of 4H-cyclohepta- and 4H-cyclopenta[b]furans (4 and 5) have been accomplished employing the intramolecular [3+2] dipolar cycloaddition based fused furan construction strategy. Treatment of the oximes (20 and 29), readily prepared from the carboxylic acid (7 and 23) via a conventional sequence of reactions, with aqueous sodium hypochlorite produced excellent yields of the isoxazolines (21 and 30), which, after alkaline hydrolysis or desilylation, were exposed to the conditions of reductive hydrolysis followed by acid-catalyzed cyclization to give the corresponding fused furans (4 and 5) in good overall yields.