Boronate‐Type‐Controlled Regioselective Catalytic [2 + 2 + 2] Cyclotrimerization for Synthesis of Polysubstituted 2‐ and 3‐Borylated Pyridines

Regioselective synthesis is a crucial concept in organic chemistry, enabling the selective formation of different regioisomers from the same type of starting materials. This approach is particularly valuable in pharmaceutical and materials sciences, where the arrangement of functional groups influences the biological activities and properties of the molecule. Pyridines are ubiquitous in organic chemistry due to their prevalence in natural products and pharmaceuticals. In addition, the introduction of boron substituents into pyridine rings enables subsequent functionalization further enhancing their utility. Herein, we present a synthetic strategy for the selective formation of either 2‐ and 3‐polysubstituted borylated pyridines via Ru‐ and Co‐catalyzed [2 + 2 + 2] cyclotrimerization reactions. Efficient synthesis and utilization of functionalized diynes allow the exploration of their reactivity in cyclotrimerization reactions with a wide variety of nitriles. The broad applicability of the methods to form pyridines with high efficiency and regioselectivity based on the used type of boronic acid derivative is shown. The application includes successful photocatalyzed cyclizations as well as the implementation of one‐pot cyclotrimerization‐coupling protocols. The findings not only provide a practical route to valuable borylated pyridines but also offer insights into the mechanistic aspects governing selectivity in these reactions.