Catalytic Diastereo- and Enantioselective Cyclopropanation of gem-Dihaloalkanes and Terminal Olefins.

Chiral cyclopropane derivatives are essential in synthetic chemistry and drug discovery. Their synthesis commonly relies on asymmetric cyclopropanation of diazo compounds, potentially explosive and needing stabilizing substituents. Thus, asymmetric catalytic transformations of non-stabilized carbenes or carbenoids remain a formidable challenge. Herein, we report the unprecedented chromium-catalyzed asymmetric cyclopropanation of readily available gem-dihaloalkanes and terminal olefins. Distinct from previous approaches, gem-dihaloalkanes serve as suitable precursors for non-stabilized carbenes or carbenoids, furnishing various functionalized chiral cyclopropanes. Mechanistic studies, including radical trapping, non-linear effect, and UV/Vis spectroscopy, provide insights into the catalytic process, featuring radical-polar crossover.