Palladium/iodide catalyzed oxidative carbonylation of aniline to diphenylurea: Effect of ppm amounts of iron salts

Pd Nanoparticles and Mixture of CO2/CO/O2 Applied in the Carbonylation of Aniline

“…Increasing amount of iodine results in higher conversion, selectivity and TOF values, with the maximum at 0.04-0.12 mmoL of I 2 (entry 9 and 10, Table 1). This observation, in agreement with previous reports [1,[59][60][61][62], indicates that iodine might play various crucial roles such as: (i) recovery of the catalytic system, perhaps by oxidation of iron powder to iron(II), (ii) generation of palladium complexes [Pd(CO) 3 I] − , considered to be the catalytically active species, (iii) reoxidation of Pd(0) to Pd(II). However, if a large excess of iodine is used, the yield of DPU decreases, and the TOF value decreases (entry 11, Table 1).…”

“…In agreement with our report [15], Fe(0) is oxidized by I 2 to Fe(II) and the possible role of Fe(II) is to react with Pd black in order to return Pd black to the catalytic cycle as shown in Scheme 1. In the literature, we can find reports for [1] and against [65] the suggested role of iron. Lower conversion of aniline, when excess of iron is used, can be attributed to the reaction between iron and oxygen, which in turn decreases the amount of necessary oxidizing agent (O 2 ).…”

“…PdNPs stabilized by 4MePy were synthesized in water, following the procedure [43,50]. Before NPs are used as catalysts they are dried because the presence of excess H 2 O in the reaction mixture might diminish the yield of diphenylurea formed during the carbonylation of aniline by CO/O 2 (partial hydrolysis of urea may occur at high temperature) [1]. The TEM images presented in Figure 2 indicate agglomeration after drying (left panel versus middle panel), therefore, we also decided to synthesize NPs in ethanol.…”

“…Environment-friendly organic synthesis is the main challenge of modern science in order to meet the objectives of sustainable development. Among many types of functionalization, insertion of a single carbonyl group into an organic molecule plays a special role due to large-scale demand for carbonyl compounds [1,2]. Excellent examples of products (both commodities and specialty chemicals) with carbonyl groups are urea derivatives, widely used in modern chemical industry-they find application in the production of pesticides (herbicides, fungicides), resin precursors, and fiber dyes [3,4], as well as antiviral and anticancer agents and other pharmaceuticals [4][5][6][7][8].…”

“…Unfortunately, dominating technologies of production of diphenylureas from aromatic amines are based on the phosgene method [9,10], and the real challenge in this sector of industry is to replace them by phosgene-free methods. The most common approaches involve less environmentally harmful carbonylating agents such as CO or alkyl carbonates [1,3,5,[11][12][13], including carbonylation performed in beneficial nonconventional solvents such as ionic liquids [12,13]. The main limitation of CO-based methods is the high pressure applied.…”