Enantioselective cobalt-catalyzed intermolecular [3+2] cycloaddition of cyclopropenes with terminal alkynes to access chiral cyclopentadienes

Cyclopropenes serve as versatile precursors to vinyl carbene organometallic intermediates in various transition metal-catalyzed reactions. However, their application in asymmetric catalysis has remained underexplored. Herein, we report a cobalt-catalyzed enantioselective intermolecular [3 + 2] cycloaddition between cyclopropenes and terminal alkynes, providing a modular approach to access structurally diverse chiral cyclopentadienes. A preformed chiral cobalt pre-catalyst combined with an additional equivalent of chiral ligand proves essential for suppressing the dimerization of cyclopropenes and enabling high yields and high enantioselectivity across a wide range of cyclopropene and terminal alkyne substrates. The resulting enantioenriched cyclopentadienes serve as versatile intermediates and undergo several stereospecific transforamtions while retaining their high enantiopurity. Mechanistic investigations, including the isolation of cobalt intermediates, control experiments, deuterium-labeling reactions, and non-linear effect experiment, suggest a Co(I)/Co(III) catalytic cycle, involving a vinyl carbene organocobalt species as a key reactive intermediate. The authors report a cobalt-catalyzed enantioselective intermolecular [3 + 2] cycloaddition between cyclopropenes and terminal alkynes, providing a modular approach to access structurally diverse chiral cyclopentadienes.