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Palladium-catalyzed synthesis of N,N'-diphenylurea from nitrobenzene, aniline, and carbon monoxide

N,N'-Diphenylurea has been synthesized from nitrobenzene, aniline, and carbon monoxide in a batch reactor at 80-160 o C and 15-75 bar. Homogeneous catalyst systems consisting of a palladium(II) salt, an onium salt, and triphenylphosphine dissolved in xylene or toluene were found to be highly efficient, giving isolated urea yields up to 98% at 100% nitrobenzene conversion. The effects of catalyst composition and other reaction variables were studied