Lewis-Acid-Catalyzed Rearrangement of Arylvinylidenecyclopropanes:  Significant Influence of Substituents and Electronic Nature of Aryl Groups

Abstract

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.

Synthesis of Novel Dimeric Allylpalladium(II) Complexes from PdCl2-Promoted Ring-Opening Reactions of Vinylidenecyclopropanes

“…Furthermore, we have recently also disclosed that the ring-opening reaction of MCPs and VDCPs could take place to give the corresponding ring-opened products under mild conditions in the presence of Lewis acids such as BF 3 ·OEt 2 , MCl n (M = Al, Zn or Sn etc), or Ln(OTf) m (Ln = Yb, Sm, Sc, La, etc.) . These interesting results stimulated us to further investigate the reactions of PdCl 2 with VDCPs 1 .…”