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Paper | Regular issue | Vol 55, No. 9, 2001, pp.1711-1725
Published online, 1st January, 1970
DOI: 10.3987/COM-01-9277
Regioselectivity in Formal [3+2] Cycloaddition Reaction of 5-Alkoxyoxazoles with Diethyl Oxomalonate and 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone

Hiroyuki Suga,* Xiaolan Shi, Toshikazu Ibata, and Akikazu Kakehi

*Department of Chemistry and Material Engineering, Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan

Abstract

Tin(IV) chloride-catalyzed formal [3 + 2] cycloaddition of 5-alkoxy-2-(p-methoxyphenyl)- or 2-phenyloxazoles with diethyl oxomalonate gave 4,5,5-tris(alkoxycarbonyl)-2-oxazolines in high regioselectivity. Under similar conditions, 4-substituted 5-alkoxy-2-methyloxazoles showed a trend to shift the regioselectivity in favor for 3-oxazolines rather than 2-oxazolines. Reaction of 5-alkoxy-4-ethoxycarbonyloxazoles with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone proceeded only under high pressure to give 2-oxazolines exclusively.