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■ Thermal Addition Reaction of Aroylketene with Ethyl Vinyl Ether: Aromatic Substituent Effect on Aroylketene Reactivity

Jun Toda, Toshiaki Saitoh, Taichi Oyama, Yoshie Horiguchi, and Takehiro Sano

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

Abstract

A series of aroylketenes (2) generated by thermolysis of 5-aryl-2,3-dihydrofuran-2,3-diones (1) reacted with ethyl vinyl ether under a thermal condition to give 2,3-dihydro-4H-pyran-4-ones (3) and/or 4H-pyran-4-ones (4). In this reaction the electron withdrawing substituent (No₂, Cl) introduces into the aryl part enhanced the ketene reactivity (2b-e), while the electron donating one (OMe) did not affect its reactivity (2f-g) in a significant extent. The heteroaroylketenes (2h) and (2i) showed a fairly good reactivity.