Songbo He

Palladium-catalyzed cross-coupling of internal alkenes with terminal alkenes to functionalized 1,3-butadienes using C-H bond activation: efficient synthesis of bicyclic pyridones.

Transition-metal-catalyzed cross-coupling through C H bond activation is emerging as one of the most important tools for carbon–carbon bond formation. In general, vinylogous compounds can be synthesized by Wittig, Heck, and Suzuki reactions, from the condensation of carbonyl compounds, C H addition to alkynes, or by means of organometallic alkenyl compounds, but direct alkenylation using C H bond activation remains particularly attractive for constructing carbon–carbon double bonds owing to their synthetic simplicity and use of readily available reagents. Vinylborates, vinyl halides, alkenyl acetates, and cyclic 1,3-dicarbonyls have been known for the direct alkenylation of arene and (hetero)arene C H bonds. In a more simple and synthetically useful alkenylation, terminal alkenes have been applied as the coupling partners. However, little attention has been paid to the direct alkenylation of alkenyl C H bonds with an alkene as the coupling partner using C H bond activation. 1,3-Butadienes, as a class of versatile organic synthetic reagents, have usually been prepared by indirect methods. To date, only two reports have been documented for their direct synthesis, involving coupling two simple terminal alkenes, owing to the difficulty in activating two alkene substrates at the same time (Scheme 1). Although two examples involving the reaction of 3-methyl-1H-indenes with tert-butyl acrylate were also reported, no work has been directed to the direct alkenylation of open-chain internal alkenes with another alkene as the coupling partner. In order to realize the direct cross-coupling of an internal alkene with a terminal alkene, the low reactivity of an internal alkenyl C H bond should be overcome. We envisioned the introduction of a structural element that could increase the reactivity of an internal alkenyl C H bond. Thus, we hypothesized that a 1,2-dithiane group at the terminal position of an alkene should satisfy the requirement on activating an internal alkenyl C H bond, and a-oxoketene dithioacetals were chosen as the internal alkenes. Herein, we report the palladium(II)-catalyzed direct cross-coupling of a-oxoketene dithioacetals with terminal alkenes as well as the synthesis of bicyclic pyridones [Eq. (1)].

Pt-Sn/γ-Al2O3-catalyzed highly efficient direct synthesis of secondary and tertiary amines and imines.

Versatile syntheses of secondary and tertiary amines by highly efficient direct N-alkylation of primary and secondary amines with alcohols or by deaminative self-coupling of primary amines have been successfully realized by means of a heterogeneous bimetallic Pt-Sn/γ-Al(2)O(3) catalyst (0.5 wt % Pt, Pt/Sn molar ratio=1:3) through a borrowing-hydrogen strategy. In the presence of oxygen, imines were also efficiently prepared from the tandem reactions of amines with alcohols or between two primary amines. The proposed mechanism reveals that an alcohol or amine substrate is initially dehydrogenated to an aldehyde/ketone or NH-imine with concomitant formation of a [PtSn] hydride. Condensation of the aldehyde/ketone species or deamination of the NH-imine intermediate with another molecule of amine forms an N-substituted imine which is then reduced to a new amine product by the in-situ generated [PtSn] hydride under a nitrogen atmosphere or remains unchanged as the final product under an oxygen atmosphere. The Pt-Sn/γ-Al(2)O(3) catalyst can be easily recycled without Pt metal leaching and has exhibited very high catalytic activity toward a wide range of amine and alcohol substrates, which suggests potential for application in the direct production of secondary and tertiary amines and N-substituted imines.

The degradation of Isophorone by catalytic wet air oxidation on Ru/TiZrO4

The catalyst Ru/TiZrO(4) was applied in the degradation of Isophorone by catalytic wet air oxidation. Mathematical models for the effects of reaction conditions on the Isophorone degradation by catalytic wet air oxidation were developed using a response surface methodology. A model was obtained for each response with multiple regression analysis and then was refined. Analysis of variance revealed that the models developed were adequate. The validity of the models was also verified by experimental data. Analysis of response surface showed that total organic carbon removal and Isophorone conversion were significantly affected (P≤0.01) by reaction time, temperature and their interactions, and affected (P≤0.05) by the square of reaction time. The point of zero charge of Ru/TiZrO(4) catalyst was about 1.72. The total organic carbon removal and Isophorone conversion had a great association with the zeta potential of Ru/TiZrO(4) catalyst. Finally, the degradation pathway of Isophorone in catalytic wet air oxidation was proposed. Within 410 h, the total organic carbon removal remained above 95%, indicating that the Ru/TiZrO(4) catalyst had a good stability.

Effect of Alumina Support on Catalytic Performance of Pt-Sn/Al2O3 Catalysts in One-Step Synthesis of N-Phenylbenzylamine from Aniline and Benzyl Alcohol

The effect of alumina on the catalytic performance of Pt‐Sn/Al2O3 catalysts in the green synthesis of secondary amines by N‐alkylation of amines with alcohols based on the borrowing hydrogen strategy was investigated. N‐alkylation of aniline with benzyl alcohol to produce N‐phenylbenzylamine was used as a model reaction. Three different alumina supports were selected, and the corresponding catalysts were prepared by complex impregnation under vacuum. The supports and catalysts were characterized using N2 adsorption‐desorption, mercury intrusion porosimetry, X‐ray diffraction, transmission electron and scanning electron microscopies, CO chemisorption, H2 temperature‐programmed reduction, and NH3 temperature‐programmed desorption. The results show that the catalysts with small Pt particles that were highly dispersed on the alumina supports and interacted weakly with the supports had high catalytic activities. The large pore volumes and pore size distributions of the alumina supports helped diffusion and adsorption of the reactants on the catalyst surface and increased the catalytic activity; they also promoted removal of the products from the catalyst surface and enhanced the catalytic stability. However, strong acidity and acid distribution of the alumina supports decreased the selectivity for secondary amines and reduced the catalyst stability.

Effect of Ce addition on the surface properties and n-dodecane dehydrogenation performance of Pt-Sn/Ce-Al2O3 catalyst

Ce-modified alumina carriers with different Ce content were prepared by vacuum isovolume impregnation method aiming to improve the n-dodecane catalytic dehydrogenation performance of PtSn/Al2O3 catalyst. The support and catalyst were characterized by XRD, N2 adsorption-desorption, NH3-TPD, H2-TPR, CO-pulse adsorption and TG-DTG. Results showed that Ce addition decreased the surface acid amount significantly and inhibited the reduction of SnOx species. Besides, Ce containing catalyst showed higher n-dodecane dehydrogenation activity and stability and lower coke deposition amount and coke burning temperature. In our study, the optimal Ce addition amount for n-dodecane dehydrogenation was 2%.

Catalytic wet peroxide oxidation of m-cresol over Fe/γ-Al2O3 and Fe-Ce/γ-Al2 O3

Catalytic wet peroxide oxidation (CWPO) of m-cresol over Fe/γ-Al2O3 and Fe-Ce/γ-Al2O3 was studied. Catalysts were prepared using the incipient wetness impregnation method, and characterized using XRD, XPS, BET, and SEM techniques. Effects of Ce loading, H2O2 dose, initial solution pH, reaction temperature, and m-cresol concentration on the CWPO of m-cresol were investigated in detail. The results showed that an addition of 2 mass % Ce into Fe/7-Al2O3 resulted in better catalytic activity over a wider pH range and at lower reaction temperatures, and with lower H2O2 consumption than when using the Fe/γ-Al2O3 catalysts only. The best catalytic activity was obtained using the Fe-Ce-2 catalyst with complete m-cresol degradation, 43.2 % TOC removal using 100 mmol L−1 H2O2 at pH 4.0 and 60°C in 90 min. XPS showed that an addition of 2 mass % Ce increased the density of non-lattice oxygen on the catalyst surface facilitating electron transfer and thereby producing radicals and promoting catalytic activity in the CWPO reaction. Recycling experiments showed that Fe-Ce-2 retained its activity even after six subsequent runs without changing the morphology, and that iron ions did not significantly leach from the catalyst surface.

Catalytic wet peroxide oxidation of m -cresol over Fe/ γ -Al 2 O 3 and Fe-Ce/ γ -Al 2 O 3

Catalytic wet peroxide oxidation (CWPO) of m-cresol over Fe/γ-Al2O3 and Fe-Ce/γ-Al2O3 was studied. Catalysts were prepared using the incipient wetness impregnation method, and characterized using XRD, XPS, BET, and SEM techniques. Effects of Ce loading, H2O2 dose, initial solution pH, reaction temperature, and m-cresol concentration on the CWPO of m-cresol were investigated in detail. The results showed that an addition of 2 mass % Ce into Fe/7-Al2O3 resulted in better catalytic activity over a wider pH range and at lower reaction temperatures, and with lower H2O2 consumption than when using the Fe/γ-Al2O3 catalysts only. The best catalytic activity was obtained using the Fe-Ce-2 catalyst with complete m-cresol degradation, 43.2 % TOC removal using 100 mmol L−1 H2O2 at pH 4.0 and 60°C in 90 min. XPS showed that an addition of 2 mass % Ce increased the density of non-lattice oxygen on the catalyst surface facilitating electron transfer and thereby producing radicals and promoting catalytic activity in the CWPO reaction. Recycling experiments showed that Fe-Ce-2 retained its activity even after six subsequent runs without changing the morphology, and that iron ions did not significantly leach from the catalyst surface.

Catalytic wet peroxide oxidation of m-cresol over Fe/gamma-Al2O3 and Fe-Ce/gamma-Al2O3

Catalytic wet peroxide oxidation (CWPO) of m-cresol over Fe/γ-Al2O3 and Fe-Ce/γ-Al2O3 was studied. Catalysts were prepared using the incipient wetness impregnation method, and characterized using XRD, XPS, BET, and SEM techniques. Effects of Ce loading, H2O2 dose, initial solution pH, reaction temperature, and m-cresol concentration on the CWPO of m-cresol were investigated in detail. The results showed that an addition of 2 mass % Ce into Fe/7-Al2O3 resulted in better catalytic activity over a wider pH range and at lower reaction temperatures, and with lower H2O2 consumption than when using the Fe/γ-Al2O3 catalysts only. The best catalytic activity was obtained using the Fe-Ce-2 catalyst with complete m-cresol degradation, 43.2 % TOC removal using 100 mmol L−1 H2O2 at pH 4.0 and 60°C in 90 min. XPS showed that an addition of 2 mass % Ce increased the density of non-lattice oxygen on the catalyst surface facilitating electron transfer and thereby producing radicals and promoting catalytic activity in the CWPO reaction. Recycling experiments showed that Fe-Ce-2 retained its activity even after six subsequent runs without changing the morphology, and that iron ions did not significantly leach from the catalyst surface.