Directed Cu(I)-Catalyzed Carbomagnesiation of 1-Arylcycloprop-2-ene-1-carboxamides En Route to Densely Substituted Functionalized Cyclopropanes.

Copper-catalyzed, directed addition of Grignard reagents across the strained C═C bond of cyclopropene-3-carboxamides was developed. It was demonstrated that the amide functionality serves as an ultimate directing group allowing for highly efficient control of diastereoselectivity of addition including stereoselectivity of electrophilic trapping with prochiral aldehydes. Also, regioselectivity of carbomagnesiation of cyclopropenes with a monosubstituted double bond is investigated. It was shown that in many cases this selectivity is controlled by steric factors and allows for preparation of products with a "reversed" regiochemistry.