The reaction of diazo ketones in the presence of metal chelates. VIII. The stereochemistry of the 1,3-dipolar cycloaddition of 1-methoxy-2-benzopyrylium-4-olates to ethylenic dipolarophiles.
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概要
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1,3-Dipolar cycloadducts were obtained in the reactions of 1-methoxy-2-benzopyrylium-4-olate (<B>3a</B>) with ethylenic dipolarophiles, such as dimethyl fumarate, dimethyl maleate, maleic anhydride, <I>trans</I>-1,2-dibenzoylethylene, <I>N</I>-substituted maleimides, and acenaphthylene. The configuration of the adducts was determined on the basis of the NMR coupling pattern of the methine protons of the adducts in connection with a deuterium experiment. The previously reported structure of the adduct of <B>3a</B> with dimethyl fumarate was corrected according to the experimental results obtained using 3-deuterated <B>3a</B>. The stereospecificity of the cycloaddition was confirmed in the reactions of dimethyl fumarate, dimethyl maleate, and <I>trans</I>-1,2-dibenzoylethylene; this stereospecificity was explained by the concerted (<SUB>π</SUB>2<SUB>S</SUB>+<SUB>π</SUB>4<SUB>S</SUB>) mechanism. The <I>exo/endo</I> ratios of the adducts of <I>N</I>-substituted maleimides may be explained by the combination of the steric repulsion and π-π interaction of the phenyl ring of <B>3</B> and the substituent on the <I>N</I>-atom of maleimides. The cycloadditions of 1-methoxy-3-methyl-2-benzopyrylium-4-olate with <I>N</I>-substituted maleimides were also explained in a similar manner.
- 公益社団法人 日本化学会の論文
著者
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Ibata Toshikazu
Institute Of Chemistry College Of General Education Osaka University
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Tsubokura Yoshie
Institute of Chemistry, College of General Education, Osaka University
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Jitsuhiro Kimiko
Institute of Chemistry, College of General Education, Osaka University
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