摘要:
A comparison of the regioselectivities for monocyclopropanation of limonene and 4-vinylclohexene using diiodomethane with zinc dust and copper(I) chloride in ether, with diethylzinc in toluene, or with triethylaluminum in toluene-dichloromethane has been carried out. Some studies were also done using dibromomethane with zinc dust and copper(I) chloride in ether. The procedure using diethylzinc in toluene exhibited the least steric hindrance toward cyclopropanation at more highly substituted, electron-rich double bonds. In a study of solvent effects on the diiodomethane, zinc dust, and copper(I) chloride procedure, use of diisopropyl ether as a reaction solvent proved to be a satisfactory method for almost doubling the steric requirements of the cyclopropanating reagent.