(+)-Limonene is a renewable chemical with numerous and growing applications. Its traditional uses such as flavor, fragrance and green solvent are rapidly expanding to include its utilization as a platform chemical, extraction solvent for natural products and an active agent for functionalized products. We anticipate that the expansion in uses for limonene will translate into increasing production and use of this relevant natural product, especially for advanced applications.
A large number of immobilized-Pd-catalysts for cross-coupling reactions have been introduced in the last decade. Are the observed catalyzed reactions truly heterogeneous or are they homogeneous due to leached palladium? This account critically addresses the leaching issue by selectively referring to some of the newly developed catalytic systems in an attempt to evaluate said systems based on uniform criteria. The report is concluded by identifying the relevant chemical and structural challenges in the field
We have found that the utilization of carbon nanotubes as support for ruthenium nanoparticles increases hydrogenation activity over 40 times in terms of turnover frequency (TOF) when compared to activated carbon in the transformation of hydroxymethylfurfural to dimethylfuran. Catalysts based on carbon nanotubes produced 83.5% yield of dimethylfuran (TOF 819.7 h −1 ) in under 1 h at 150 °C and less than 20 bar hydrogen pressure, whereas the activated carbon catalyst required more than 3 h to give an 80% yield of dimethylfuran (TOF 36 h −1 ). The superior accessibility of pores in carbon nanotubes, plus an electronic promotional effect in the carbon nanotubes, appear to be responsible for the superior activity of the catalysts supported on carbon nanotubes. The catalysts were synthesized by impregnation and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, nitrogen physisorption, temperature-programmed reduction, electron microscopy and pulse CO chemisorption to propose the structure−activity relationships. This work highlights the importance of the support in hydrogenating reactions with ruthenium and the potential applicability of carbon nanotubes as supports for the hydrogenation of other bioderivatives.
A new series of leach-proof nanostructured Pd(0) catalysts able to catalyze a number of fundamental organic transformations including C–C bond formation has been developed. Reactions in general proceed with high yield and often at completion, while the catalysts can be reused in further reaction runs. This establishes a new class of relevant solid catalysts for synthetic organic chemistry trademarked SiliaCat Pd0 Hydrogel
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