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Communication | Regular issue | Vol 4, No. 8, 1976, pp.1355-1360
Published online, 1st January, 1970
DOI: 10.3987/R-1976-08-1355
■ Diels-Alder Reaction in a Polar System. Thermal Cycloaddition of 1-Phenyl-2-ethoxycarbonyl-3-benzoyl-Δ2-pyrroline-4,5-dione with Butadienes

Yoshisuke Tsuda,* Yoshie Horiguchi, and Takehiro Sano

*Showa Pharmaceutical University, 3-3165, Higashi-tamagawagakuen, Machida, Tokyo 194-8543, Japan

Abstract

In thermal reactions of 1-phenyl-2-ethoxycarbonyl-3-benzoyl-Δ2-pyrroline-4,5-dione (1) with butadienes, two types of [4+2] cycloaddition were observed. One was a formation of pyrano-pyrrole derivative (type A), where butadiene behaved as a dienophile and pyrroline-4,5-dione as a diene. The other was an usual Diels-Alder product (type B). The type A adduct thermally rearranged in a [3,3lsigmatropic manner into the type B adduct. 1-Acetoxy-, 1-sulphenyl-, and 1-trimethylsilyloxy butadienes also cycloadded to 1 and afforded only type B adducts, which were suggested to be formed from the initially generated type A adducts. The similar phenomenon was observed in the cycloaddition reaction of 1 with norbornadiene.