Theoretical studies of samarium carbenoid promoted cyclopropanation reaction with allylic alcohol on the reaction pathways

The density functional theory was employed to investigate the mechanism for the cyclopropanation reactions of samarium carbenoid with an allylic alcohol. Seven competitive reaction pathways were investigated. Analysis of the calculated results shows that the models 4 and 6 have relatively low reaction barriers which suggested that the deprotonation of allylic alcohol promoted by CH₃SmCH₂I plays a significant important role in the cyclopropanation reaction via a samarium carbenoid. The methylene transfer and carbometalation pathways are involved in both intermolecular and intramolecular reaction pathways. On the basis of the energetics of the reaction pathways, the methylene transfer pathway is favored over the carbometalation pathway in the whole reactions. Our computational results are in good agreement with the experimental results performed by G.A. Molander and L.S. Harring.