Polymer Encapsulated Cobalt‐Based Catalysts (Co EnCatTM) for Selective Continuous Hydrogenation of 1‐Iodo‐4‐nitrobenzene

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. Polyurea microencapsulated Co catalysts: Cobalt and cobalt/nickel encapsulated in a polyurea matrix show high selectivity to 4‐iodoaniline and low levels of dehalogenation in the hydrogenation of 1‐iodo‐4‐nitrobenzene. The low level of dehalogenation makes this material interesting for the hydrogenation of nitroaromatics bearing labile groups as substituents on the phenyl ring. Catalytic performance depends on metal loading and type of alloy used for the catalyst preparation.