Isodiiodomethane is the methylene transfer agent in cyclopropanation reactions with olefins using ultraviolet photolysis of diiodomethane in solutions: A density functional theory investigation of the reactions of isodiiodomethane, iodomethyl radical, and iodomethyl cation with ethylene

We examine the chemical reactions of the isodiiodomethane (CH2I-I), . CH2I and CH2I+ species with ethylene using density functional theory computations. The CH2I-I species readily reacts with ethylene to give the cyclopropane product and an I-2 product via a one-step reaction with a barrier height of similar to2.9 kcal/mol. However, the . CH2I and CH2I+ species have much more difficult pathways (with larger potential barriers) to react with ethylene via a two-step reaction mechanism. Comparison of experimental results to our present calculation results indicates that the CHI-I photoproduct species is most likely the methylene transfer agent for the cyclopropanation reaetion of olefins via ultraviolet photoexcitation of diiodomethane.