Simmons-Smith cyclopropanation
Abstract
The Simmons-Smith cyclopropanation is a reaction in which an alkene is converted into a cyclopropane upon treatment with diiodomethane and zinc.
Keywords
Alkene, Diiodomethane, Zinc, Cyclopropane
Category
Alkene
Mechanism
First, zinc reacts with diiodomethane in a oxidative addition step to give an organozinc carbenoid species. This intermediate undergoes syn addition across the double bond of the alkene. During this step, a butterfly-shaped transition state is formed, in which the methylene group is delivered to both faces of the alkene simultaneously. Finally, after elimination of zinc iodide, the cyclopropane ring is obtained. Key point: The Simmons-Smith cyclopropanation is a stereospecific reaction, meaning that the geometry of the starting alkene is fully retained in the final product.
Recent review
Munir, R.; Zahoor, A. F.; Javed, S.; Parveen, B.; Mansha, A.; Irfan, A.; Kotwica-Mojzych, K.; Mojzych, M. Simmons–Smith cyclopropanation: a multifaceted synthetic protocol toward the synthesis of natural products and drugs: a review. Molecules. 2023, 28, 5651.