<i>Cine</i> ‐Reductive Carboboration of Alkenyl Electrophiles via Iron Catalysis

In traditional transition-metal-catalyzed cross-coupling reactions, alkenyl electrophiles typically undergo transformation at the ipso-position of the leaving group, resulting in the formation of a single bond, rather than the installation of two functionalities across a C═C unit. Achieving the direct difunctionalization of alkenyl electrophiles has become increasingly desirable for streamlining the synthesis of complex molecules, which is essential for advancing molecular complexity in organic synthesis. Here, we report an iron-catalyzed cine-reductive carboboration of alkenyl tosylates with alkyl halides, providing a streamlined route to synthetically valuable tetrasubstituted alkenyl boronates. Mechanistic studies support a pathway that involves selective cine-alkylation of alkenyl tosylates followed by borylation, enabling the sequential formation of C(sp³)─C(sp³) and C(sp³)─B bonds, with subsequent elimination affording the desired C(sp²)─C(sp²) and C(sp²)─B bonds. These findings not only provide new mechanistic insights into iron-catalyzed cine-coupling processes but also establish a foundation for the rational design of new transformations of alkenyl electrophiles under iron catalysis.