Dirhodium-Catalyzed Enantioselective Synthesis of Difluoromethylated Cyclopropanes via Enyne Cycloisomerization

(Difluoromethylated cyclopropane represents an important motif, which is widely found in bioactive and functional molecules. Despite significant progress in modern chemistry, the atom-economic and enantioselective synthesis of difluoromethylated cyclopropanes is still challenging. Herein, an Rh2(II)-catalyzed asymmetric enyne cycloisomerization is described to construct chiral difluoromethylated cyclopropane derivatives with up to 99% yield and 99% ee in low catalyst loading (0.2 mol%), which can be easily transformed into highly functionalized difluoromethylated cyclopropanes with vicinal all-carbon quaternary stereocenters by ozonolysis. Mechanistic studies and the crystal structures of alkyne-dirhodium complexes reveal that the cooperative weak hydrogen bondings between the substrates and the dirhodium catalyst may play key roles in this reaction.) A Rh2(II)-catalyzed asymmetric enyne cycloisomerization to construct chiral difluoromethylated cyclopropane derivatives is reported, which can be easily transformed into highly functionalized difluoromethylated cyclopropanes with vicinal all-carbon quaternary stereocenters through ozonolysis. Mechanistic studies and the X-ray crystal structures of alkyne-dirhodium complexes reveal that the cooperative weak hydrogen bondings between the substrates and the dirhodium catalyst may play key roles in this reaction.image

Automated summary

This study reports a Rh2(II)-catalyzed asymmetric enyne cycloisomerization for the synthesis of chiral difluoromethylated cyclopropane derivatives, which can be easily transformed into highly functionalized difluoromethylated cyclopropanes with vicinal all-carbon quaternary stereocenters through ozonolysis. Mechanistic studies and X-ray crystallography of alkyne-dirhodium complexes suggest that cooperative weak hydrogen bondings between the substrates and the dirhodium catalyst may be crucial in this reaction.