Construction of Fused Polycyclic System via Tandem Cationic Cyclization by Using the Properties of Fluorine

利用氟的性质通过串联阳离子环化构建稠合多环体系

• 批准号: 14540488
• 负责人: ICHIKAWA Junji
• 金额: $ 2.3万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2002
• 资助国家: 日本
• 起止时间: 2002 至 2003
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14540488/
• 关键词: carbocation; difluoroalkene; transitionmetal complex; fused polycycclic compound; SN2' reaction; cationic cyclization; Friedel-Crafts cyclization; helicene; 遷移金属錯本; SN2'反応; プロトン酸; 縮合環; 二環式ケトン; タンデム環化

Fluorine possesses (i) leaving-group ability as fluoride ion(F^-) and (ii) α-cation-stabilizing effect due to its lone pairs. Our interest in using these two properties prompted us to investigate the generation of fluorine-containing carbocations from 1,1-difluoroalkenes, which would allow ring constructions by intramolecular trapping of the cations with unsaturated groups, followed by F^-elinination. Thus, we have accomplished fluorine-promoted Friedel-Crafts cyclization of 1,1difluoro-1-dalkenes bearing two aryl groups via α-fluorocarbocations, generated by the regioselective protonation of the fluorinated double bonds, leading to the construction of fused polycyclic systems. Moreover, this cyclization has proved to be effected eve by transition metal complexes instead of strong protic acids.The SN"' reaction of 4-ary-2-trifluoromethyl-q-butenes and benzyl anions affords 1,1-difluoro-1-alkenes with two aryl groups at appropriate positions. Treatment of thus obtained difluoroalkenes with FSO_3H/SbF_5 or Pd(BF_4)_2(MeCN)_4 in (CF_3)_CHOH (HFIP) readily promotes intramolecular Friedel-Crafts reactions. The tandem cyclizations successfully proceed to afford fused polycyclic compounds, whose dehydrogenation with palladium hydroxide on activated carbon leads to [4]helicenes in high yield.The sequence of reactions: the SN2' reaction, the tandem cationic cyclizations, and the dehydrogenation affords fused polycyclic compounds such as helicenes in only three steps from the 1-trifluoromethyl vinyl compounds. Since most of helicenes have been prepared via photo cyclization of stilbene moieties, developing a methodology for supplying large amount of helicenes have been a desirable goal. The results disclosed herein open a new approach to helicenes including functionalized ones.

氟具有（i）作为氟离子（f^ - ）和（ii）α-结式稳定作用的（i）离开组的能力，这是由于其孤对。我们对使用这两种特性的兴趣促使我们研究了1,1-二氟烷烃从1,1-二氟烷基中产生含氟的碳，这将通过分子内捕获阳离子以不饱和基团的形式进行环构建，然后进行F^ - 释放。这就是我们完成了1,1difluoro-1-dalkenes的氟促进的Friedel-Crafts循环，该烯基通过α-氟化碳纤维源，这是由荧光双键的调节质子化产生的，从而导致了融合多晶系统的构建。此外，通过过渡金属复合物而不是强烈的蛋白质，这种环化已被证明是有效的夏娃。 Sn“'4- ARY-2-三氟甲基-Q丁二烯和苄基阴离子的反应可在适当位置使用两个芳基的1,1-二氟-1-烯烃。因此，使用FSO_3H/SBF_5或PD（BF_4）_3（BF_4）_3（MECN）_3（MECN）_4（MECN）i（MEC）（MECN）i（MEC）（MEC）（MECN）i（MEC）（MEC）（MEC）（MEC）（MECN）IN（MECN）（MEC）容易促进分子内弗里德尔工艺反应。诸如从1-三氟甲基乙烯基化合物的三个步骤中，由于大多数螺旋素是通过对Silbene部分的光环制备的。