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.