Selective Synthesis of Primary Anilines from NH 3 and Cyclohexanones by Utilizing Preferential Adsorption of Styrene on the Pd Nanoparticle Surface

Dehydrogenative aromatization is one of the attractive alternative methods for directly synthesizing primary anilines from NH 3 and cyclohexanones. However, the selective synthesis of primary anilines is quite difficult because the desired primary aniline products and the cyclohexanone substrates readily undergo condensation affording the corresponding imines (i.e., N ‐cyclohexylidene‐anilines), followed by hydrogenation to produce N ‐cyclohexylanilines as the major products. In this study, primary anilines were selectively synthesized in the presence of supported Pd nanoparticle catalysts (e.g., Pd/HAP, HAP=hydroxyapatite, Ca 10 (PO 4 ) 6 (OH) 2 ) by utilizing competitive adsorption unique to heterogeneous catalysis; in other words, when styrene was used as a hydrogen acceptor, which preferentially adsorbs on the Pd nanoparticle surface in the presence of N ‐cyclohexylidene‐anilines, various structurally diverse primary anilines were selectively synthesized from readily accessible NH 3 and cyclohexanones. The Pd/HAP catalyst was reused several times though its catalytic performance gradually declined.