Trace amount of single-atom palladium-catalyzed selective hydrosilylation of allenes

Using fewer catalysts to promote the chemical conversion of more substrates is the dream synthesis pursued by synthetic chemists. Achieving highly selective reactions using trace amounts (< 1 ppm) of catalysts is rare and has undoubted practical value. Herein, we designed and synthesized a single-atom Pd-metalated porous organic ligand polymer, denoted as Pd₁@POL, and used the polymer to realize the regioselective hydrosilylation of allenes (Pd loading was as low as 0.98 ppm). The synergistic effect of the dispersed catalytic active sites in the catalyst and supports with ligand regulation function can directionally realize the formation of specifically configured hydrosilylation products. The as-fabricated single-atom catalyst (SAC; i.e., Pd₁@POL-5) showed an amazing catalytic efficiency and selectivity for hydrosilylation of allene (turnover number was up to 772,358, which was 200 times higher than previously recorded, and regioselectivity > 100:1). The catalyst could be recycled numerous times in a continuous flow system without reductions in activity and selectivity. This work demonstrated the application prospect of the SAC in the synthesis of complex organic compounds and trace amount catalysis, which can lay the foundation for its large-scale and industrialized application in drug synthesis and other fields.