MOFs as multifunctional catalysts: One-pot synthesis of menthol from citronellal over a bifunctional MIL-101 catalyst

A bifunctional MOF catalyst containing coordinatively unsaturated Cr3+ sites and palladium nanoparticles (Pd@MIL-101) has been used for the cyclization of citronellal to isopulegol and for the one-pot tandem isomerization/hydrogenation of citronellal to menthol. The MOF was found to be stable under the reaction conditions used, and the results obtained indicate that the performance of this bifunctional solid catalyst is comparable with other state-of-the-art materials for the tandem reaction: Full citronellal conversion was attained over Pd@MIL-101 in 18 h, with 86% selectivity to menthols and a diastereoselectivity of 81% to the desired (-)-menthol, while up to 30 h were necessary for attaining similar values over Ir/H-beta under analogous reaction conditions.Financial support by Ministerio de Educacion y Ciencia e Innovacion (Project MIYCIN, CSD2009-00050; PROGRAMA CONSOLIDER. INGENIO 2009), Generalidad Valenciana (GV PROMETEO/2008/130) and the CSIC (Proyectos Intramurales Especiales 201080I020) is gratefully acknowledged.García Cirujano, F.; Llabrés I Xamena, FX.; Corma Canós, A. (2012). MOFs as multifunctional catalysts: One-pot synthesis of menthol from citronellal over a bifunctional MIL-101 catalyst. Dalton Transactions. 41:4249-4254. https://doi.org/10.1039/c2dt12480gS4249425441Corma, A., García, H., & Llabrés i Xamena, F. X. (2010). Engineering Metal Organic Frameworks for Heterogeneous Catalysis. Chemical Reviews, 110(8), 4606-4655. doi:10.1021/cr9003924Farrusseng, D., Aguado, S., & Pinel, C. (2009). Metal-Organic Frameworks: Opportunities for Catalysis. Angewandte Chemie International Edition, 48(41), 7502-7513. doi:10.1002/anie.200806063Lee, J., Farha, O. K., Roberts, J., Scheidt, K. A., Nguyen, S. T., & Hupp, J. T. (2009). Metal–organic framework materials as catalysts. 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Science, 309(5743), 2040-2042. doi:10.1126/science.1116275Corma, A., & Renz, M. (2004). Sn-Beta zeolite as diastereoselective water-resistant heterogeneous Lewis-acid catalyst for carbon–carbon bond formation in the intramolecular carbonyl–ene reaction. Chem. Commun., (5), 550-551. doi:10.1039/b313738dIosif, F., Coman, S., Pârvulescu, V., Grange, P., Delsarte, S., Vos, D. D., & Jacobs, P. (2004). Ir-Beta zeolite as a heterogeneous catalyst for the one-pot transformation of citronellal to menthol. Chem. Commun., (11), 1292-1293. doi:10.1039/b403692aNeaţu, F., Coman, S., Pârvulescu, V. I., Poncelet, G., De Vos, D., & Jacobs, P. (2009). Heterogeneous Catalytic Transformation of Citronellal to Menthol in a Single Step on Ir-Beta Zeolite Catalysts. Topics in Catalysis, 52(9), 1292-1300. doi:10.1007/s11244-009-9270-9MERTENS, P., VERPOORT, F., PARVULESCU, A., & DEVOS, D. (2006). Pt/H-beta zeolites as productive bifunctional catalysts for the one-step citronellal-to-menthol conversion. 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Sunlight-assisted hydrogenation of CO2 into ethanol and C2+ hydrocarbons by sodium-promoted Co@C nanocomposites

[EN] The hydrogenation of CO2 into hydrocarbons promoted by the action of sunlight has been studied on Co nanoparticles covered by thin carbon layers. In particular, nearly 100% selectivity to hydrocarbons is obtained with increased selectivities towards C2 + hydrocarbons and alcohols (mainly ethanol) when using nanostructured materials comprising metallic cobalt nanoparticles, carbon layers, and sodium as promoter (NaCo@C). In the contrary, larger amount of CH4 and lower selectivity to C2 + hydrocarbons and alcohols were obtained in the conventional thermal catalytic process. When using Co@C nanoparticles in the absence of Na or bare Co3O4 as catalyst, methane is essentially the main product (selectivity > 96%). Control experiments in the presence of methanol as a hole scavenger suggest the role of light in generating charges by photon absorption as promoting factor. The reaction mechanism for photoassisted CO2 hydrogenation on the Co-based catalysts was investigated by near ambient-pressure X-ray photoelectron (AP-XPS) and in situ Raman spectroscopies, which provided information on the role of light and Na promoter in the modulation of product distribution for CO2 hydrogenation. Spectroscopic studies suggested that surface CO2 dissociation to CO, the stabilization of CO adsorbed on the surface of Na-Co@C catalyst and the easy desorption of reaction products is a key step for photothermal CO2 hydrogenation to ethanol and C2 + hydrocarbons.L.L. thanks ITQ for providing a contract. A.V.P. thanks the Spanish Government (Agencia Estatal de Investigacion) and the European Union (European Regional Development Fund) for a grant for young researchers (CTQ2015-74138-JIN, AEI/FEDER/UE). J.C. thanks the Spanish Government-MINECO for a "Severo Ochoa" grant (BES-2015-075748). The AP-XPS experiments were performed at NAPP endstation of CIRCE beamline at ALBA Synchrotron with the collaboration of ALBA staff. The authors also thank the Microscopy Service of UPV for kind help on FESEM, TEM and STEM measurements. Financial supports from the Spanish Government-MINECO through "Severo Ochoa" (SEV-2016-0683) program are also gratefully acknowledged.Liu, L.; Puga, AV.; Cored-Bandrés, J.; Concepción Heydorn, P.; Pérez-Dieste, V.; García Gómez, H.; Corma Canós, A. (2018). Sunlight-assisted hydrogenation of CO2 into ethanol and C2+ hydrocarbons by sodium-promoted Co@C nanocomposites. Applied Catalysis B Environmental. 235:186-196. https://doi.org/10.1016/j.apcatb.2018.04.060S18619623

On the Synergistic Catalytic Properties of Bimetallic Mesoporous Materials Containing Aluminum and Zirconium: The Prins Cyclisation of Citronellal

Bimetallic three-dimensional amorphous mesoporous materials, Al-Zr-TUD-1 materials, were synthesised by using a surfactant-free, one-pot procedure employing triethanolamine (TEA) as a complexing reagent. The amount of aluminium and zirconium was varied in order to study the effect of these metals on the Brønsted and Lewis acidity, as well as on the resulting catalytic activity of the material. The materials were characterised by various techniques, including elemental analysis, X-ray diffraction, high-resolution TEM, N2 physisorption, temperature-programmed desorption (TPD) of NH3, and 27Al MAS NMR, XPS and FT-IR spectroscopy using pyridine and CO as probe molecules. Al-Zr-TUD-1 materials are mesoporous with surface areas ranging from 700–900 m2 g−1, an average pore size of around 4 nm and a pore volume of around 0.70 cm3 g−1. The synthesised Al-Zr-TUD-1 materials were tested as catalyst materials in the Lewis acid catalysed Meerwein–Ponndorf–Verley reduction of 4-tert-butylcyclohexanone, the intermolecular Prins synthesis of nopol and in the intramolecular Prins cyclisation of citronellal. Although Al-Zr-TUD-1 catalysts possess a lower amount of acid sites than their monometallic counterparts, according to TPD of NH3, these materials outperformed those of the monometallic Al-TUD-1 as well as Zr-TUD-1 in the Prins cyclisation of citronellal. This proves the existence of synergistic properties of Al-Zr-TUD-1. Due to the intramolecular nature of the Prins cyclisation of citronellal, the hydrophilic surface of the catalyst as well as the presence of both Brønsted and Lewis acid sites synergy could be obtained with bimetallic Al-Zr-TUD-1. Besides spectroscopic investigation of the active sites of the catalyst material a thorough testing of the catalyst in different types of reactions is crucial in identifying its specific active sites

Homogeneous and heterogeneous catalysts for multicomponent reactions

[EN] Organic synthesis performed through multicomponent reactions is an attractive area of research in organic chemistry. Multicomponent reactions involve more than two starting reagents that couple in an exclusive ordered mode under the same reaction conditions to form a single product which contains the essential parts of the starting materials. Multicomponent reactions are powerful tools in modern drug discovery processes, because they are an important source of molecular diversity, allowing rapid, automated and high throughput generation of organic compounds. This review aims to illustrate progress in a large variety of catalyzed multicomponent reactions performed with acid, base and metal heterogeneous and homogeneous catalysts. Within each type of multicomponent approach, relevant products that can be obtained and their interest for industrial applications are presented.The authors wish to gratefully acknowledge the Generalitat Valenciana for the financial support in the project CONSOLIDER-INGENIO 2010 (CSD2009-00050)Climent Olmedo, MJ.; Corma Canós, A.; Iborra Chornet, S. (2012). Homogeneous and heterogeneous catalysts for multicomponent reactions. RSC Advances. 2(1):16-58. https://doi.org/10.1039/c1ra00807bS16582

Photobiocatalysis: The Power of Combining Photocatalysis and Enzymes

Photobiocatalysts are constituted by a semiconductor with or without a light harvester that activates an enzyme. A logical source of inspiration for the development of photobiocatalysts has been natural photosynthetic centers. In photobiocatalysis, the coupling of the semiconductor and the enzyme frequently requires a natural cofactor and a relay transferring charge carriers from the semiconductor. The most widely studied photobiocatalysts so far make use of conduction band electrons of excited semiconductors to promote enzymatic reductions mediated by NAD(+)/NADH and an electron relay. The present review presents the state of the art in the field and has been organized based on the semiconductor and the reaction type including oxidations, hydrogen generation, and CO2 reduction. The possibility of direct enzyme activation by the semiconductor and the influence of the nature of mediator are also discussed as well as the use of mimics of the enzyme active center in combination with the semiconductor. The final section summarizes the state of the art of photobiocatalysis and comments on our view on future developments of the field.Financial support by the Spanish Ministry of Economy and Competitiveness (Severo Ochoa and CTQ2012-32315) is gratefully acknowledged. J.A.M.-A. acknowledges the assistance of the CSIC for the award of a Postdoctoral JAE-Doc contract co-financed by the European Social Fund.Maciá Agulló, JA.; Corma Canós, A.; García Gómez, H. (2015). Photobiocatalysis: The Power of Combining Photocatalysis and Enzymes. Chemistry - A European Journal. 21(31):10940-10959. https://doi.org/10.1002/chem.201406437S1094010959213

Effects of Anacetrapib in Patients with Atherosclerotic Vascular Disease

BACKGROUND: Patients with atherosclerotic vascular disease remain at high risk for cardiovascular events despite effective statin-based treatment of low-density lipoprotein (LDL) cholesterol levels. The inhibition of cholesteryl ester transfer protein (CETP) by anacetrapib reduces LDL cholesterol levels and increases high-density lipoprotein (HDL) cholesterol levels. However, trials of other CETP inhibitors have shown neutral or adverse effects on cardiovascular outcomes. METHODS: We conducted a randomized, double-blind, placebo-controlled trial involving 30,449 adults with atherosclerotic vascular disease who were receiving intensive atorvastatin therapy and who had a mean LDL cholesterol level of 61 mg per deciliter (1.58 mmol per liter), a mean non-HDL cholesterol level of 92 mg per deciliter (2.38 mmol per liter), and a mean HDL cholesterol level of 40 mg per deciliter (1.03 mmol per liter). The patients were assigned to receive either 100 mg of anacetrapib once daily (15,225 patients) or matching placebo (15,224 patients). The primary outcome was the first major coronary event, a composite of coronary death, myocardial infarction, or coronary revascularization. RESULTS: During the median follow-up period of 4.1 years, the primary outcome occurred in significantly fewer patients in the anacetrapib group than in the placebo group (1640 of 15,225 patients [10.8%] vs. 1803 of 15,224 patients [11.8%]; rate ratio, 0.91; 95% confidence interval, 0.85 to 0.97; P=0.004). The relative difference in risk was similar across multiple prespecified subgroups. At the trial midpoint, the mean level of HDL cholesterol was higher by 43 mg per deciliter (1.12 mmol per liter) in the anacetrapib group than in the placebo group (a relative difference of 104%), and the mean level of non-HDL cholesterol was lower by 17 mg per deciliter (0.44 mmol per liter), a relative difference of -18%. There were no significant between-group differences in the risk of death, cancer, or other serious adverse events. CONCLUSIONS: Among patients with atherosclerotic vascular disease who were receiving intensive statin therapy, the use of anacetrapib resulted in a lower incidence of major coronary events than the use of placebo. (Funded by Merck and others; Current Controlled Trials number, ISRCTN48678192 ; ClinicalTrials.gov number, NCT01252953 ; and EudraCT number, 2010-023467-18 .)