Birch-Type Reduction of Arenes in 2-Propanol Catalyzed by Zero-Valent Iron and Platinum on Carbon

Rh-catalyzed mechanochemical transfer hydrogenation for the synthesis of periphery-hydrogenated polycyclic aromatic compounds

Hydrogenated nanographene has attracted attention as a new class of nanocarbon material owing to its potential applications in various research fields. However, the synthesis of periphery-hydrogenated nanographenes or polycyclic aromatic hydrocarbons (PAHs) is a significant challenge because of the harsh conditions and poor solubility of the starting materials. Conventional solution-state conditions require high-pressure hydrogen gas and lengthy reaction times. In this study, we developed a novel approach utilizing rhodium-catalyzed mechanochemical transfer hydrogenation, which enables hydrogenation without using hydrogen gas. Various hydrogenated PAHs were rapidly obtained using a simple protocol under ambient atmosphere and air, with one PAH showcasing intriguing properties such as aggregation-induced emission. Thus, the demonstrated mechanochemical hydrogenation method is expected to contribute to the rapid and efficient synthesis of a novel class of sp2/sp3-carbon-conjugated hydrocarbons.

Remediation of Saline Wastewater Producing a Fuel Gas Containing Alkanes and Hydrogen Using Zero Valent Iron (Fe0)

Zero valent iron (Fe0) water remediation studies, over the last 40 years, have periodically reported the discovery of CnH2n+2 in the product water or product gas, where n = 1 to 20. Various theories have been proposed for the presence of these hydrocarbons. These include: (i) reductive transformation of a more complex organic chemical; (ii) hydrogenation of an organic chemical, as part of a degradation process; (iii) catalytic hydrogenation and polymerisation of carbonic acid; and (iv) redox transformation. This study uses wastewater (pyroligneous acid, (pH = 0.5 to 4.5)) from a carbonization reactor processing municipal waste to define the controls for the formation of CnH2n+2 (where n = 3 to 9), C3H4, and C3H6. A sealed, static diffusion, batch flow reactor, containing zero-valent metals [181 g m-Fe0 + 29 g m-Al0 + 27 g m-Cu0 + 40 g NaCl] L−1, was operated at two temperatures, 273–298 K and 348 K, respectively. The reactions, reactant quotients, and rate constants for the catalytic formation of H2(g), CO2(g), C3H4(g), C3H6(g), C3H8(g), C4H10(g), C5H12(g), C6H14(g,l), and C7H16(g,l), are defined as function of zero valent metal concentration (g L−1), reactor pressure (MPa), and reactor temperature (K). The produced fuel gas (422–1050 kJ mole−1) contained hydrogen + CnHy(gas), where n = 3 to 7. The gas production rate was: [1058 moles CnHy + 132 moles H2] m−3 liquid d−1 (operating pressure = 0.1 MPa; temperature = 348 K). Increasing the operating pressure to 1 MPa increased the fuel gas production rate to [2208 moles CnHy + 1071 moles H2] m−3 liquid d−1. In order to achieve these results, the Fe0, operated as a “Smart Material”, simultaneously multi-tasking to create self-assembly, auto-activated catalysts for hydrogen production, hydrocarbon formation, and organic chemical degradation (degrading carboxylic acids and phenolic species to CO2 and CO).

Chemoselective and Tandem Reduction of Arenes Using a Metal-Organic Framework-Supported Single-Site Cobalt Catalyst

The development of heterogeneous, chemoselective, and tandem catalytic systems using abundant metals is vital for the sustainable synthesis of fine and commodity chemicals. We report a robust and recyclable single-site cobalt-hydride catalyst based on a porous aluminum metal-organic framework (DUT-5 MOF) for chemoselective hydrogenation of arenes. The DUT-5 node-supported cobalt(II) hydride (DUT-5-CoH) is a versatile solid catalyst for chemoselective hydrogenation of a range of nonpolar and polar arenes, including heteroarenes such as pyridines, quinolines, isoquinolines, indoles, and furans to afford cycloalkanes and saturated heterocycles in excellent yields. DUT-5-CoH exhibited excellent functional group tolerance and could be reusable at least five times without decreased activity. The same MOF-Co catalyst was also efficient for tandem hydrogenation-hydrodeoxygenation of aryl carbonyl compounds, including biomass-derived platform molecules such as furfural and hydroxymethylfurfural to cycloalkanes. In the case of hydrogenation of cumene, our spectroscopic, kinetic, and density functional theory (DFT) studies suggest the insertion of a trisubstituted alkene intermediate into the Co-H bond occurring in the turnover limiting step. Our work highlights the potential of MOF-supported single-site base-metal catalysts for sustainable and environment-friendly industrial production of chemicals and biofuels.

Mild and Selective Rhodium-Catalyzed Transfer Hydrogenation of Functionalized Arenes

Diboron-mediated rhodium-catalyzed transfer hydrogenation of functionalized arenes is reported. In addition to good functional group tolerance, the reaction features operational simplicity and controllable chemoselectivity. The general applicability of this procedure is demonstrated by the selective hydrogenation of a range of arenes, including functionalized benzenes, biphenyls, and polyaromatics.