HCo(PMe ₃ ) ₄ ‐Catalyzed 1,2‐Selective Hydroboration of Quinolines: Access to Isolable N–B and N–H 1,2‐Dihydroquinolines

Well‐defined cobalt hydride complexes can be versatile catalysts that enable a wide range of transformations. In this work, we highlight two important aspects of the hydroboration of quinolines catalyzed by HCo(PMe 3 ) 4 . First, we report its previously unexplored reactivity toward the highly selective 1,2‐hydroboration of quinolines, providing direct access to N–B‐substituted 1,2‐dihydroquinolines (1,2‐DHQs). This transformation proceeds efficiently under mild catalytic conditions and represents a selective route to partially reduced quinoline derivatives. Second, we demonstrate that the simplicity of HCo(PMe 3 ) 4 , which contains volatile phosphine ligands and displays high solubility in pentane, enables a straightforward purification strategy for the resulting products. As a result, the N–B‐protected 1,2‐DHQs can be isolated in pure form, whereas they have previously been described mainly as crude intermediates. Importantly, these borylated compounds exhibit significantly improved stability over time compared to the corresponding N–H 1,2‐DHQs, which are known to prone disproportionation pathway over time. The N–B derivatives can be readily stored and manipulated, making them convenient synthetic intermediates. Furthermore, they provide straightforward access to the corresponding N–H 1,2‐DHQs through simple alcoholysis. This approach therefore offers a practical entry to otherwise unstorable N–H 1,2‐dihydroquinolines and expands the synthetic utility of cobalt hydride catalysis in quinoline functionalization.