Iridium-catalyzed doubly stereoconvergent allylic alkylation of racemic α-boryl organozinc reagents

Summary Transition-metal-catalyzed allylic alkylation of α -boryl metallic reagents has provided unique access to chiral homoallylic organoboron compounds . However, these organoboron products possess only one stereogenic center, which is derived exclusively from either allylic electrophiles or gem -diborylalkanes. The construction of contiguous stereocenters from both α -boryl metallic reagents and allylic electrophiles has remained elusive. We report a straightforward method to prepare secondary α -monoboryl organozinc reagents through α -deprotonation of benzylboronates and in situ Li/Zn exchange that was then applied in the iridium-catalyzed allylic alkylation reaction through a doubly stereoconvergent process. Various boron-containing 1,2-stereodiads were obtained in good yields with decent diastereo- and enantioselectivities . Compared to the deborylative allylic alkylation using gem -diborylalkane, this study demonstrates high atom economy and a wide substrate scope. A preliminary mechanism study demonstrated that the stereoconvergent and kinetic resolutions of racemic carbonates proceed simultaneously.