Phosgene Free Synthesis of N, N’ Diphenylurea via Oxidative Carbonylation of Aniline by using a Multistep Electron Transfer Catalytic System

Ureas are a very important class of carbonyl compounds which find extensive application as agrochemicals, dyes for cellulose fibers, antioxidants in gasoline, resin precursors, and farmaceuticals. Moreover, N, N'-diphenylurea (DPU) has been extensively studied for application as synthetic intermediates especially for the phosgene-free production of carbamates and isocyanates, whose importance both in industrial and academic fields is well known. Phosgene is a toxic, corrosive, expensive, and difficult to handle raw material and its substitution in the industrial processes where it is used with more sustainable reaction routes represent an important target. It is thus natural that a great deal of research has been directed toward a convenient alternative phosgene-free route for many industrial processes. The catalytic carbonylation of aniline appears as a convenient alternative green synthesis of DPU without using phosgene. Several are the catalytic system proposed in literature, both homogeneous and heterogeneous. The main objective of this paper is to identify and optimize a new homogeneous Pd(II)-based catalytic systems for such reaction.