Anion-Mediated, Stereospecific Synthesis of Secondary and Tertiary Cyclopropylboronates from Chiral Epoxides and gem -Diborylalkanes.

We report a transition-metal-free deborylative cyclization approach to synthesize enantioenriched secondary and tertiary cyclopropylboronates using γ-phosphate-containing -diborylalkanes derived from chiral epoxides and -diborylalkanes. Our method enables the synthesis of a broad range of enantioenriched secondary and tertiary cyclopropylboronates in good yields with excellent stereospecificity. We demonstrate the versatility of our approach by performing a gram-scale reaction. We also show that the enantioenriched tertiary cyclopropylboronates can be transformed into a wide array of enantioenriched cyclopropane derivatives in a stereospecific boron-group transformation.