Indazole enhances Ru-catalyzed hydrogenation of unsaturated bonds†

The catalytic hydrogenation process is highly coveted and holds high potential due to its efficient conversion of crucial molecules into environmentally friendly alcohols, showcasing exceptional atom efficiency and selectivity. Moreover, these alcohol products serve as versatile precursors for synthesizing various pharmaceuticals. Herein, we have developed a practical and efficient procedure for the hydrogenation of various unsaturated compounds using Ru-catalysis with an indazole backbone PNN pincer ligand. This method effectively tackles the challenge of chemoselectivity in multifunctional hydrogenation reactions involving CC/N/O and CC bonds. The Ru catalytic system exhibits exceptional performance in the scalable synthesis of PNN ligands, achieving a turnover number of 63 371 and producing 146.18 grams of alcohol with a catalyst concentration as low as 0.001 mol%.