Stereoselective Hydroxyallylation of Cyclopropenes with Cyclopropanols via NHC Catalysis of Transient Organozinc Species

A stereoselective hydroxyallylation reaction of cyclopropenes with cyclopropanols is achieved under zinc-mediated conditions, affording densely functionalized cyclopropanes with excellent diastereocontrol over three contiguous stereocenters within and outside the cyclopropane ring. A racemic variant of the reaction is synergistically promoted by catalytic N-heterocyclic carbene (NHC) and organic base (DBU), whereas chiral amino alcohol-derived bifunctional NHC enables a catalytic enantioselective variant. Mechanistically, the reaction features transient generation of enolized zinc homoenolate via ring-opening of zinc cyclopropoxide and enolization of the resulting homoenolate, followed by its addition to the cyclopropene as a prochiral allylzinc nucleophile.