Polystyrene or Magnetic Nanoparticles as Support in Enantioselective Organocatalysis? A Case Study in Friedel-Crafts Chemistry

Heterogenized versions of the second generation MacMillan imidazolidin-4-one are described for the first time. This versatile organocatalyst has been supported onto 1% DVB Merrifield resin and Fe3O4 magnetic nanoparticles through copper-catalyzed alkyne-azide cycloaddition (CuAAC) reaction. The resulting catalytic materials have been successfully applied to the asymmetric Friedel- Crafts alkylation of indoles with &alpha;,&beta;-unsaturated aldehydes. While both catalytic systems can be easily recovered and admit repeated recycling, the polystyrene-based catalyst shows higher stability and provides better stereoselectivities.</p

Synthesis of 2-Methylpyrazine Using Crude Glycerol over Zn-Cr-O Catalyst: A Value Addition Process for the Utilization of Biodiesel By-Product

Mixed oxides of ZnO and Cr2O3 with varied mole ratios were synthesized, characterized, and evaluated for the dehydrocyclization of crude glycerol for the production of 2-methylpyrazine (2-MP). The Zn-Cr-O composition was optimized using the bulk and surface properties of the catalysts rationalized by BET-SA, XRD, XPS, H2-TPR, O2 pulse chemisorption, and Raman spectroscopic techniques to achieve a high rate of 2-MP

Spillover Hydrogen on Electron-Rich Ni/m-TiO2 for Hydrogenation of Furfural to Tetrahydrofurfuryl Alcohol

Conversion of biomass-derived furfural (FFA) platform molecule to value-added tetrahydrofurfuryl alcohol (THFA) molecule is a sustainable route using an efficient non-noble metallic catalyst in water solvent. In this work, Ni in various loadings on mesoporous titanium dioxide (m-TiO2) was synthesized in one pot by Evaporation-Induced Self-Assembly (EISA). The synthesised catalysts were evaluated for the hydrogenation of furfural to tetrahydrofurfuryl alcohol. The catalysts were characterised using a combination of spectroscopic techniques such as XRD, H2-TPR, H2-TPD, XPS, SEM-EDX, TEM, and HR-TEM. The characterization results show that the Ni/m-TiO2 materials exhibit enhanced electron-rich active sites, facilitated hydrogen spillover, uniform dispersion of small Ni particles (~5 nm), and strong metal support interaction between Ni and TiO2. Among the various Ni dopings, 7.5 wt.% Ni/m-TiO2 catalyst exhibited the best performance and achieved 99.9% FFA conversion and 93.2% THFA selectivity in water solvent at 100 &deg;C and under 2 MPa H2. Additionally, detailed kinetic studies, process parameters, the stability and reusability of the catalyst were also studied. The results demonstrated that the 7.5 wt.% Ni/m-TiO2 catalyst is highly active and stable

Spillover Hydrogen on Electron-Rich Ni/m-TiO₂ for Hydrogenation of Furfural to Tetrahydrofurfuryl Alcohol

Conversion of biomass-derived furfural (FFA) platform molecule to value-added tetrahydrofurfuryl alcohol (THFA) molecule is a sustainable route using an efficient non-noble metallic catalyst in water solvent. In this work, Ni in various loadings on mesoporous titanium dioxide (m-TiO2) was synthesized in one pot by Evaporation-Induced Self-Assembly (EISA). The synthesised catalysts were evaluated for the hydrogenation of furfural to tetrahydrofurfuryl alcohol. The catalysts were characterised using a combination of spectroscopic techniques such as XRD, H2-TPR, H2-TPD, XPS, SEM-EDX, TEM, and HR-TEM. The characterization results show that the Ni/m-TiO2 materials exhibit enhanced electron-rich active sites, facilitated hydrogen spillover, uniform dispersion of small Ni particles (~5 nm), and strong metal support interaction between Ni and TiO2. Among the various Ni dopings, 7.5 wt.% Ni/m-TiO2 catalyst exhibited the best performance and achieved 99.9% FFA conversion and 93.2% THFA selectivity in water solvent at 100 °C and under 2 MPa H2. Additionally, detailed kinetic studies, process parameters, the stability and reusability of the catalyst were also studied. The results demonstrated that the 7.5 wt.% Ni/m-TiO2 catalyst is highly active and stable

Synthesis of acetyl-substituted tetrahydrobenzofuran and tetrahydronaphthalene via cascade Diels-Alder cycloadditions and dehydration of renewable furanics

A acetyl-substituted tetrahydrobenzofuran, 1-(4,5,6,7-tetrahydro-1-benzofuran-6-yl)ethenone (6-AcBZOF) and a acetyl-substituted tetrahydronaphthalene, 1-(1,2,3,4-tetrahydronaphthalen-2-yl)ethenone (2-AcTNAPH) were conveniently synthesized from renewable furanics by cascade Diels-Alder and dehydration reactions. The Diels-Alder cycloaddition of 4-(2-Furyl)-3-buten-2-one (4-FB) with ethylene followed by dehydration in presence of zeolites was studied. Sn grafted Beta zeolite exhibited high performance with 69% yield of 2-AcTNAPH starting from 4-FB. In this reaction, 6-AcBZOF was produced as intermediate. Further, it was found that this acetyl substituted tetrahydrobenzofuran could be formed in high yield, 86%, in the absence of catalyst. For the first time in the literature, we report the synthesis of a renewable acetyl-substituted tetrahydronaphthalene in high yield from biomass-derived 4-FB in a tandem approach. While a acetyl-substituted tetrahydrobenzofuran could be prepared without a catalyst, catalyst was essential for the successful synthesis of the acetyl-substituted tetrahydronaphthalene

C-H bond cyanation of arenes using N,N-dimethylformamide and NH4HCO3 as a CN source over a hydroxyapatite supported copper catalyst

A hydroxyapatite supported Cu catalyst [HAP:Ca(PO)(OH)] has been found to be an efficient and reusable heterogeneous catalyst for safe cyanation of C–H bonds of hetero aryl compounds. The combination of NHHCO and DMF is identified as a CN source under mild reaction conditions. 10 wt% Cu/HAP offered good to excellent yields compared to Ru/HAP and Pd/HAP catalysts. The surface basicity and Cu metal surface area of the catalysts played a significant role in the cyanation reaction through C–H bond activation. The catalyst was recovered and reused for five cycles showing consistent activity and selectivity. The physicochemical characteristics of the catalysts are rationalized by H-TPR, BET-SA, XPS, TEM and NO titration techniques