Zhang Yun-Peng, Lu Jian-Mei, Xu Guang-Cai, Shi Min
School of Chemistry & Molecular Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China.
J Org Chem. 2007 Jan 19;72(2):509-16. doi: 10.1021/jo061899r.
Lewis-acid-catalyzed reactions of arylvinylidenecyclopropanes having three substituents at the corresponding cyclopropyl rings have been investigated thoroughly. The reaction products are highly dependent on the substituents at the corresponding cyclopropyl rings and the electronic nature of the aryl groups. For arylvinylidenecyclopropanes bearing two alkyl groups at the C-1 position (R1, R2, R3=aryl; R4=H; R5, R6=alkyl), naphthalene derivatives were formed in the presence of Lewis-acid Eu(OTf)3 in DCE at 40 degrees C. For arylvinylidenecyclopropanes in which R1, R2, R3=aryl and R4, R5=alkyl (syn/anti isomeric mixtures), the corresponding 6aH-benzo[c]fluorine derivatives were formed in the syn-configuration via a double intramolecular Friedel-Crafts reaction when all of the aryl groups do not have electron-withdrawing groups or the corresponding indene derivatives were obtained via an intramolecular Friedel-Crafts reaction as long as one electron-deficient aryl group was attached. For arylvinylidenecyclopropanes in which R1, R2, R3, R4=aryl and R5=alkyl or H, the corresponding indene derivatives were obtained exclusively via a sterically demanding intramolecular Friedel-Crafts reaction. Lewis-acid effects and mechanistic insights have been discussed on the basis of experimental investigations.
对相应环丙基环上具有三个取代基的芳基乙烯基环丙烷的路易斯酸催化反应进行了深入研究。反应产物高度依赖于相应环丙基环上的取代基以及芳基的电子性质。对于在C-1位带有两个烷基的芳基乙烯基环丙烷（R1、R2、R3 = 芳基；R4 = H；R5、R6 = 烷基），在40℃的二氯乙烷中，在路易斯酸Eu(OTf)3存在下形成萘衍生物。对于R1、R2、R3 = 芳基且R4、R5 = 烷基（顺式/反式异构体混合物）的芳基乙烯基环丙烷，当所有芳基都没有吸电子基团时，通过双分子内傅克反应以顺式构型形成相应的6aH-苯并[c]芴衍生物，或者只要连接有一个缺电子芳基，就通过分子内傅克反应得到相应的茚衍生物。对于R1、R2、R3、R4 = 芳基且R5 = 烷基或H的芳基乙烯基环丙烷，仅通过空间要求较高的分子内傅克反应得到相应的茚衍生物。基于实验研究讨论了路易斯酸的作用和机理见解。
