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化学学报
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化学学报 ›› 1987, Vol. 45 ›› Issue (9): 904-909. 上一篇    下一篇

研究论文

一个异常的反应-顺式的二氟芪与二氟卡宾反应生成反式的环加成物

计国桢;陈国飞;吴宗美;蒋锡夔   

  1. 中国科学院上海有机化学研究所
  • 发布日期:1987-09-15

The formation of trans cycloadduct from the reaction of difluorocarbene with cis-difluorostilbene

JI GUOZHEN;CHEN GUOFEI;WU ZONGMEI;JIANG XIKUI   

  • Published:1987-09-15

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478

在光敏剂(丁二酮,0.05mol.dm^-^3)存在下,75%的反式1,2-二氟芪通过光化学异构化转化成顺式1,2-二氟芪,由Seyferth试剂(PhHgCF3)产生的二氟卡宾(CF2)与顺式和反式芪的反应是立体专一性环加成反应,遵循Skell规则.然而,尽管CF2与反式1,2-二氟芪反应得到反式1,2-二苯基全氟环丙烷(9),顺式1,2-二氟芪与二氟卡宾反应仍然得到相同的反式环加成物,这一异常现象,可能是由于高度活化的三元环中CF2对面的C-C键均裂而产生的.

关键词: 光化学反应, 光敏化, 苯 P, 碳烯, 环加成反应, 化学键, 有机氟化合物, 异构化反应, 取代基效应, 丁二酮

The photochem. isomerization of trans- and cis-difluorostilbene is reported. In the presence of a photosensitizer (biacetyl, 0.05 mol譫m-3) about 75% of the trans form can be converted into the crystalline cis form. The reactions of :CF2 from the Seyferth reagent (PhHgCF3) with cis- and trans-stilbene obey the Skell Rule, i.e., stereospecific cycloaddn. However, although the reaction of :CF2 with trans-1,2-difluorostilbene yields trans-1,2-diphenylperfluorocyclopropane as the only isolable product, the reaction of :CF2 with cis-1,2-difluorostilbene also gives the same trans-cycloadduct as the only isolable product. A possible mechanistic path involving the homolytic cleavage of the highly activated cyclopropane C-C bond facing the CF2 group is discussed.

Key words: PHOTOCHEMICAL REACTION, PHOTOSENSITIZATION, BENZENE P, CARBENE, CYCLOADDITION REACTION, CHEMICAL BONDS, ORGANO FLUORINE COMPOUNDS, ISOMERIZATION REACTION, SUBSTITUENT EFFECT, BUTANEDIONE

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