Abstract:A highly efficient and stable Pd-diimine@SBA-15 catalyst was successfully prepared by immobilizing Pd onto diimine-functionalized mesoporous silica SBA-15. With the help of diimine functional groups grafted onto the SBA-15, Pd could be anchored on a support with high dispersion. Pd-diimine@SBA-15 catalyst exhibited excellent catalytic performance for the Suzuki coupling reaction of electronically diverse aryl halides and phenylboronic acid under mild conditions with an ultralow amount of Pd (0.05 mol % Pd). When the catalyst amount was increased, it could catalyze the coupling reaction of chlorinated aromatics with phenylboronic acid. Compared with the catalytic performances of Pd/SBA-15 and Pd-diimine@SiO 2 catalysts, the Pd-diimine@SBA-15 catalyst exhibited higher hydrothermal stability and could be repeatedly used four times without a significant decrease of its catalytic activity.

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Palladium-catalyzed cross-coupling reaction has become one of the most powerful and convenient protocol for the construction of carbon-carbon bonds in agrochemistry, pharmaceutical chemistry, materials and synthetic chemistry. In recent years, a variety of different structures of ligands and novel catalysts have been widely explored. Wherein N-heterocyclic carbene (NHC) ligands are employed as new generation catalysts in cross-coupling reactions due to low toxicity, good stability as well as appropriate coordination ability. The application of new developed Pd-NHC catalysts in cross-coupling reactions is reviewed according to the characteristics of NHC structures.

Deuterated reagents have been used in many research fields. Isotope abundance, as the feature parameter of deuterated reagents, the precise quantification, is of great importance. Based on quantitative nuclear magnetic resonance technology, a novel method that combines 1H NMR + 2H NMR was systematically established to determine the isotopic abundance of deuterated reagents. The results showed that the isotopic abundance of partially labeled and fully labeled compounds calculated by this new method was even more accurate than that calculated by classical 1H NMR and mass spectrometry (MS) methods. In brief, this new method is a robust strategy for the determination of isotope abundance in large‐scale deuterated reagents.

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