Inducing Cu Charge Redistribution by Modulating Proximity with Zr(OH)4 for Selective Synthesis of Imines and Secondary Amines with Stoichiometric Benzyl Alcohol and Nitrobenzene

The one-pot synthesis of amines from benzyl alcohol (BA) and nitrobenzene (NB) represents a step-economic method. However, reported works typically require more than 3 equiv of BA to complete the transfer hydrogenation of NB, and few studies can achieve selective synthesis of imines and secondary amines. In our previous work, Zr(OH)4 demonstrated both hydrogenation and dehydrogenation capabilities. Building on this, another component Cu was introduced to enhance its catalytic performance for catalyzing coupling reaction between stoichiometric BA and NB under a H2 atmosphere. The physical hybrid catalyst Cu + Zr(OH)4 selectively produced imines, while the supported catalyst Cu/Zr(OH)4 yielded secondary amines. Characterization and mechanism experiments revealed that modulating the proximity between Cu and Zr(OH)4 leads to (1) different adsorption abilities of the catalyst for N-benzylideneaniline (NBA) and (2) interactions between Zr(OH)4 and Cu in close contact, which stabilized the electronic structure of Cu forming more Cu+/Cu0 ion pairs with strong H2 activation ability. This work presents a catalyst design strategy and offers an approach for the selective preparation of N-benzylideneaniline and N-benzylaniline.