The selective hydrogenation of functionalized nitroaromatics poses a major challenge from both academic as well as industrial viewpoints. As part of the CHEM21 initiative (www.chem21.eu), we are interested in highly selective, catalytic hydrogenations of halogenated nitroaromatics. Initially, the catalytic reduction of 1-iodo-4-nitrobenzene to 4-iodoaniline served as a model system to investigate commercial heterogeneous catalysts. After determining optimal hydrogenation conditions and profiling performances of the best catalysts, hydrogenations were transferred from batch to continuous flow. Finally, the optimized flow conditions were applied to transformations which represent important steps in the syntheses of the active pharmaceutical ingredients clofazimine and vismodegib.

Acarbon nanotube supported catalyst containing cobalt/cobalto xide (Co/Co 3 O 4 )n anoparticles encapsulatedw ithin as hell of nitrogen-doped graphene layers (Co 3 O 4 /NGr@CNT) was prepared. It shows excellent chemoselectivity in the hydrogenation of 1-iodo-4-nitrobenzene,w hich contains an iodine substituenth ighly sensitive against hydrodehalogenation. In contrast to traditional activated charcoal-supported catalysts such as Pt-V/C or the closely relatedV ulcan carbon black supported Co 3 O 4 /NGr@C, the advantageous morphological properties of the CNT support allow for the applica-tion of the new Co 3 O 4 /NGr@CNT as af ixed bed catalyst in ac ontinuous flow reactor. Under optimized conditions,n od ehalogenation side productsc ould be detected. This remarkable selectivity in combination with its mechanical stability under operation conditions renderC o 3 O 4 /NGr@CNT ac atalyst particularly relevant for applicationi nc ontinuousp rocesses based on apacked bed reactor.

New cobalt catalysts confined in an EnCatTM polyurea matrix by micro‐encapsulation of Al5Co2 or Al5Co2/Al3Ni2 phase containing alloys are disclosed for the reductive hydrogenation of 1‐iodo‐4‐nitrobenzene 1. The product 4‐iodo‐aniline 2 readily undergoes hydro‐desiodination and was used to demonstrate the extraordinary selectivity. Co EnCatTM significantly suppressed this follow‐up reaction under both batch and flow modes. The correlation between performance, elemental composition, and alloy content is presented for these novel catalysts. Among them, the hybrid micro‐encapsulated Co‐Ni catalyst showed higher activity than its Ni‐free analogue. In the flow process, this catalyst gave a high yield of 2 and very low level of 3. Hence, these novel Co EnCatTM catalysts hold promise with respect to the continuous‐flow hydrogenation of challenging halogenated nitroaromatic compounds.

Nanoparticles (NP) have specific catalytic properties, which are influenced by parameters like their size, shape, or composition. Bimetallic NPs, composed of two metal elements can show an improved catalytic activity compared to the monometallic NPs. We, herein, report on the selective aerobic oxidation of benzyl alcohol catalyzed by unsupported Pd/Au and Pd NPs at atmospheric pressure. NPs of varying compositions were synthesized and characterized by UV/Vis spectroscopy, transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS). The NPs were tested in the model reaction regarding their catalytic activity, stability, and recyclability in batch and continuous procedure. Additionally, in situ extended X-ray absorption fine structure (EXAFS) measurements were performed in order to get insight in the process during NP catalysis.

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