Manganese-Catalyzed Dehydrogenative Synthesis of Urea Derivatives and Polyureas

Urea derivatives have significant applications in the synthesis of resin precursors, dyes, agrochemicals, and pharmaceutical drugs. Furthermore, polyureas are useful plastics with applications in coating, adhesive, and biomedical industries. However, the conventional methods for the synthesis of urea derivatives and polyureas involve toxic reagents such as (di)isocyanates, phosgene, CO, and azides. We present here the synthesis of (poly)ureas using much less toxic reagents-(di)amines and methanol-via a catalytic dehydrogenative coupling process. The reaction is catalyzed by a pincer complex of an earthabundant metal, manganese, and liberates H2 gas, valuable by itself, as the only byproduct, making the overall process highly atomeconomic. A broad variety of symmetrical and unsymmetrical urea derivatives and polyureas have been synthesized in moderate to quantitative yields using this catalytic protocol. Mechanistic insights have also been provided using experiments and DFT computation, suggesting that the reaction proceeds via an isocyanate intermediate.

Automated summary

Urea derivatives and polyureas are important compounds with diverse applications. However, the conventional synthesis methods involving toxic reagents pose risks to the environment and human health. In this study, a catalytic reaction using safer reagents was developed to synthesize urea derivatives and polyureas. The method demonstrated high efficiency and atom economy, achieving moderate to quantitative yields of various compounds. Mechanistic insights were also provided through experiments and computational analysis.