Journal of Catalysis, Vol.374, 72-81, 2019
Competitive adsorption on PtCo/CoBOx catalysts enables the selective hydrogen-reductive-imination of nitroarenes with aldehydes into imines
Catalytic synthesis of imines from one-pot cascade hydrogen reductive imination of nitroarenes with aldehydes represents a facile, green and valuable process; however, such an economical process suffers from the poor chemoselectivity due to competitive hydrogenation of aldehydes and over-hydrogenation of imines into N-alkylated amines. Herein, bimetallic PtCo nanoparticles anchored on cobalt borate nanosheets (PtCo/CoBOx) can facilitate the unparalleled activity and selectivity towards imines through the same imination. The high chemoselectivity of imines is resulted from the competitive adsorption of reactants and products on PtCo/CoBOx, including (1) weakened adsorption of imines and its uncompetitive adsorption with aromatic amines (from nitroarenes) on bimetallic PtCo to minimize its over-hydrogenation; (2) competitive adsorption of nitroarenes on PtCo and preferential adsorption of aldehydes/nitroarenes on hydroxyl-enriched CoBOx through hydrogen bond formation to suppress hydrogenation of both aldehydes and imines; and (3) kinetically and competitively preferred reduction of nitroarenes over aldehydes to avoid hydrogenation of aldehydes. (C) 2019 Elsevier Inc. All rights reserved.