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■ [2π + 2σ] and [8π + 2σ] Types Cycloaddition Reactions of Aza-, Thio-, and Thiaza-azulen-2(1H)-one Derivatives with Naphtho[b]cyclopropene: Effects of Solvents and Ytterbium Complex

Katsuhiro Saito,* Naoko Ito, and Shinichi Ando

*Department of Applied Chemistry, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan

Abstract

Reactions of naphtho[b]cyclopropene with 1-aza- or 1-thiaazulene-2(1H )-one derivatives in chloroform under the presence of a catalytic amount of ytterbium complex afforded [2π + 2σ] type cycloaddition products. The analogous reactions of the cyclopropene with a 1-thia-3-azaazulene-2(1H )-one derivative gave an [8π + 2σ] type cycloadduct. These reactions were considered to proceed via ionic processes, in which the azulene-2(1H )-one derivatives played as 2π and 8π components, respectively. On the other hand, reactions of the cyclopropene with 1-azaazulene-2(1H )-one derivatives in benzene yielded the another type of [8π + 2σ] type cycloadducts via a concerted process.