Phosgene-free synthesis of 1,3-diphenylurea via catalyzed reductive carbonylation of nitrobenzene

Abstract

1,3-Diphenylurea (DPU) has been proposed as a synthetic intermediate for phosgene-free synthesis of methyl N-phenylcarbamate and phenyl isocyanate, which are easily obtained from the urea by reaction with methanol. Such an alternative route to synthesis of carbamates and isocyanates necessitates an improved phosgene-free synthesis of the corresponding urea. In this work, it is reported that Pd(II)-diphosphine catalyzed reductive carbonylation of nitrobenzene in acetic acid (AcOH)-methanol proceeds in high yield and selectivity as a one-step synthesis of DPU. We have found that the catalytic activity and selectivity of this process depends on solvent composition and on the bite angle of the diphosphine ligands. Under optimum reaction conditions, yields in excess of 90 molar % and near-quantitative selectivity can be achieved.

Formates for green catalytic reductions via CO2 hydrogenation, mediated by magnetically recoverable catalysts

“…The reaction proceed smoothly giving high conversion and almost quantitative yield in about 20 h of reaction. Similar results were obtained by using CO as reductant in the presence of homogeneous Pd catalyst [20]. In Fig.…”

“…As a matter of fact, the reaction gives only 1-phenylethanol, and no traces of alcohol reduction. Despite of the presence of two liquid phase, reaction arrive to completeness in 20 h suggesting an activity of the catalyst comparable to those observed in the hydrogen transfer from NaOCHO nitrobenzene catalyzed by Pd catalyst, reported in the previous section, and also in reductive carbonylation of nitrobenzene with Pd catalyst [20]. Table 2 shows the activity of various catalyst in acetophenone reduction to 1-phenylethatol.…”

“…However, the use of formates are of paramount importance because of its potentiality in attaining selectivity to carbamates and ureas, similarly to what is observed employing CO as reducing agent [20].…”

Supported Palladium Nanoparticles Catalyzed Reductive Carbonylation of Nitroarenes to N‐Arylformamides

“…The removal of CO 2 molecule and further addition of CO transform intermediate ( III ) into ( IV ) which subsequently gave rise to intermediate ( V ) after the removal of CO 2 molecule. The addition of CO to ( V ) produced intermediate ( VI ) and also ( V ) in presence of water and CO (which is present in the reaction system) may procure corresponding amine ( VII ) , . The intermediate ( VI ) gave arylisocyanate ( VIII ) which may undergo hydration and subsequent formylation or following the transfer hydrogenation approach to give final product 2 and regenerating the Pd@PS catalyst ( I ) in the process (Scheme ).…”

Intermediate formation enabled regioselective access to amide in the Pd-catalyzed reductive aminocarbonylation of olefin with nitroarene

“…The above differences in regioselectivity, reaction parameter effect, and substrate scope seem to indicate that the present selective carbonylations undergo different reaction pathways under Condition A and Condition B. It has been found that nitroarene can be catalytically reduced to nitrosoarene, aromatic amine, N-aryl hydroxylamine, and aryl isocyanate under CO atmosphere [16,17,[51][52][53]. Therefore, control reactions with these N-species would provide more insights into the present aminocarbonylation with nitroarene as N-source.…”