Reactions of diarylvinylidenecyclopropanes with bromine at −100 °C in dichloromethane and ether. A drastic solvent effect

For diarylvinylidenecyclopropanes 1 having two aromatic groups at C-1 position and one methyl group at the C-2 position of cyclopropyl ring, the reaction with bromine at low temperature (−100 °C) produces the brominated indene derivatives 2 and conjugated triene derivatives 3 in high yields in dichloromethane and ether within 10 min, respectively. This drastic solvent effect has been discussed on the basis of previous investigation.