Selective Ammonium Carbamate Crystallization: An Innovative Approach for Catalyst Recycling in Homogeneously Catalyzed Primary Amine Synthesis

Abstract Homogeneous catalysis presents an efficient strategy for the selective production of primary amines, while challenges in product and catalyst separation limit its broader application. This study introduces selective ammonium carbamate crystallization (SACC) as a novel catalyst recycling methodology. SACC is based on waste‐free and reversible salt formation between primary amines and CO 2 . These salts exhibit reduced solubility in nonpolar solvents, enabling selective product isolation by cooling‐crystallization and reuse of the catalyst‐containing filtrate. We successfully implemented this process in the first successful catalyst recycling for the homogeneously catalyzed alcohol amination for primary amine synthesis, achieving eight recycling runs and a cumulative turnover number (∑TON) of 748 for the HRuCl(CO)(PPh 3 ) 3 /Xantphos catalyst system. Water accumulation during the process was identified as a critical factor that reduces isolated yields by increasing solvent polarity. Therefore, SACC was extended to water‐free nitrile hydrogenation with two catalysts: [Ru(2‐methylallyl) 2 (cod)]/Triphos achieved five recycling runs with a ∑TON of 458, while Ru(acac) 3 /Triphos/DBU demonstrated superior stability with nine runs yielding a ∑TON of 743. Product isolation was accomplished for eight runs, yielding an excellent average purity of 97% and minimal ruthenium losses at 0.6%, underscoring the efficiency of this methodology.