Fe(0)-catalyzed radical halosulfonation: Regioselective synthesis of α-halo alkylboronic esters

• Cheap and earth-abundant iron powder as the sulfonyl radical initiator. • Fe(I)-halogen species intermediate acts as a halogen-transferring donor. • The involvement of a Fe(II) state in the catalytic cycle. • α -Halo alkylboronic esters were prepared under simple reaction conditions. α -Halo alkylboronic esters are versatile reagents in chemical synthesis. These reagents are typically prepared by the homologation of boronic esters with a dihaloalkyl lithium species. However, the need to form anionic boron intermediates limits the scope of α -haloboronates. Herein, we present a method for the catalytic radical halosulfonation of vinylboronates to a variety of α -halo alkylboronic esters using iron powder as catalyst. This protocol features functional group tolerance, wide substrate scope, gram-scale synthesis, and operational simplicity under air conditions. Moreover, the resulting products can be smoothly derivatized to various value-added molecules. The combined mechanistic investigations and density functional theory calculations suggest that Fe(I)-halogen species generated from the in situ reaction plays a key role to drive the catalytic cycle and also acts as an actual halogen-transferring donor. An iron powder catalyzed halosulfonation of vinylboronates to a variety of α -halo alkylboronic esters has been developed. This protocol features a remarkably simple reaction conditions, operational simplicity, and readily available starting materials. Also, the synthetic applications and mechanistic investigations are studied.