Copper-catalysed synthesis of chiral alkynyl cyclopropanes using enantioconvergent radical cross-coupling of cyclopropyl halides with terminal alkynes

Transition-metal-catalysed enantioconvergent cross-coupling reactions of highly reactive alkyl radicals often suffer from reduced chemoselectivity, mainly due to side reactions with closed-shell reactants. A strategy to overcome this challenge has yet to be identified, posing substantial limitations on the synthetic utility of this method. Here we report a method for enantioconvergent radical carbon–carbon cross-coupling of highly reactive cyclopropyl radicals with terminal alkynes, using redox state-tuned copper catalysis, under mild conditions. Key to this method is the use of hard chiral N,N,N-ligands in combination with Cu(II) salts of hard ligands/counterions, which results in elevated concentrations of Cu(II) species and thus enhanced cross-coupling reactions. This protocol not only exhibits a broad substrate scope across a wide range of both racemic cyclopropyl halide and terminal alkyne coupling partners but also provides access to useful yet synthetically challenging enantioenriched cyclopropane building blocks.