Density Functional Theory Investigation of the Reaction of Isodiiodomethane with Acetylene:  Potential Utility of Isodiiodomethane for Cyclopropenation Reactions

We present density functional theory calculations for the reactions of CH₂I−I and CH₂I with acetylene (HC⋮CH) to form a cyclopropene product. CH₂I−I readily reacts with HC⋮CH to form a cyclopropene product and an I₂ leaving group via a rate-determining step barrier of ∼3.9 kcal/mol (B3LYP/Sadlej-pVTZ). Calculations indicated that the CH₂I radical reacts to form an iodopropenyl radical, which can close to a cyclopropene only with difficulty. Our results indicate that CH₂I−I may act as an effective carbenoid to produce cyclopropenated products from alkynes.