Carbonylation Of Nitro Compounds Research Articles

Certain methods of activating PdCl2 catalysts for carbonylation of azo and nitro compounds

1. In the synthesis of isocyanates by carbonylation of azo and nitro compounds, it has been found that Fe, Fe2O3, FeCl3 and FeBr3 activate the PdCl2 catalyst; the Fe and Fe2O3, under the influence of the PdCl2, pass into solution in the form of Fe(II) and Fe(III) compounds. 2. Anilines, diphenylurea, water, and acetanilide (which hydrolyze metal chlorides) and the thermally unstable salts pyridine hydrochloride, ammonium chloride, and triethylamine hydrochloride promote the catalyst PdCl2 + Py in the synthesis of isocyanates by carbonylation of nitro compounds in a steel autoclave; acetic anhydride, Zn, and basic oxides inhibit this reaction; and TiO2 and SiO2 have no effect on the catalyst activity. 3. Iron acetylacetonate suppresses the carbonylation of azobenzene in the presence of the catalysts PdCl2 + py and Pd(py)2Cl2 + py.

Combined carbonylation of nitro and azo compounds in the synthesis of isocyanates

1. In the synthesis of isocyanates by the carbonylation of azo compounds, palladium chloride displays activity without promotors, organic bases inhibit the action of palladium chloride, while Lewis acids activate the palladium chloride-pyridine catalyst. 2. Azo compounds are not intermediates in the conversion of nitro compounds to isocyanates in the presence of palladium chloride and pyridine. 3. A scheme was proposed for the activating effect of amines, triphenylphosphine, and compounds of iron, molybdenum, and vanadium added to the palladium catalyst for the synthesis of isocyanates by the carbonylation of nitro compounds.

Catalytic carbonylation of nitro compounds in the presence of carbonyl ionic complexes of Rh(I), Ir(I), Pd(I), and Pd(II)

1. Anionic carbonyl halide complexes of rhodium and palladium are active homogeneous catalysts for the synthesis of aryl isocyanates by carbonylation of nitro compounds. 2. By introducing BU4NCl into the catalytic system based on palladium complexes in an amount of 1 to 2 moles per g-atom of palladium, nitrobenzene and o-nitrotoluene can be carbonylated to give a 20–25% yield of the corresponding isocyanates under carbon monoxide at atmospheric pressure.

Synthesis of carbamates by carbonylation of nitro compounds in the presence of thiourea

Synthesis of carbamates by carbonylation of nitro compounds in the presence of thiourea

Synthesis of isocyanates by the carbonylation of aromatic nitro compounds, azobenzene, and azoxybenzene on palladium catalysts containing molybdenum and vanadium

1. Nitro compounds are converted by the action of CO into isocyanates on palladium catalysts containing vanadium and molybdenum compounds bypassing the formation and carbonylation azo compounds, apparently as a result of the direct carbonylation of nitrenes. 2. The addition of Ca(VO3)2, A1(VO3)3, Pb(VO3)2, H2MoO4)2MoO4, and CdMoO4 to the PdCl2-pyridine catalytic system promote the carbonylation of nitro compounds and inhibit the conversions of azo compounds by the action of CO.

Catalytic synthesis of isocyanates by carbonylation of nitro compounds in the presence of [Rh(CO)2 Cl]2 promoted by pyridine and pyridine hydrochloride

1. Pyridine and pyridine hydrochloride activate [Rh(CO)2Cl]2 in the synthesis of isocyanates by the carbonylation of aromatic nitro compounds; in the presence of the catalyst [Rh(CO)2 Cl]2-Py-PyHCl (weight ratio 1–2∶18∶5), at 205°, a CO pressure of 50 atm, and a time of 40 min, nitrobenzene, 3-nitrotoluene, 4-chloro-nitrobenzene, and 4-methoxynitrobenzene are converted to the corresponding isocyanates in 36–90% yield. 2. The activating effect of Py and Py·HCl apparently consists in the formation from [Rh(CO)2Cl]2 of catalytically active monomeric rhodium complexes, which contain Py, Cl−, and CO as ligands.

Catalytic carbonylation of nitro compounds with carbon monoxide in presence of rhodium-carbonyl hydride complex

1. The rhodium carbonyl hydride complex RhH(CO) (PPh3)3 is an active catalyst for the synthesis of phenyl isocyanate, the o-, m-, and p-tolyl isocyanates, and mesityl isocyanate from the corresponding aromatic nitro compounds by carbonylation with CO. The optimum reaction conditions were determined (pressure, temperature, time, substrate/catalyst ratio). 2. The use of MoCl5 as a cocatalyst increases the conversion of the nitro compound, the yield of the isocyanate, and the selectivity of the process. 3. Methyl substituents in the o-position activate the nitro group when nitro compounds are carbonylated with CO.

ChemInform Abstract: CATALYTIC SYNTHESIS OF AROMATIC MONOISOCYANATES FROM NITRO COMPOUNDS AND CARBON MONOXIDE

1. We have synthesized aromatic monoisocyanates in 78–90% yield by carbonylation of nitro compounds with carbon monoxide in the presence of a PdCl2 + pyridine + V2O5, V2O4, or MoO3 catalyst at 200°C and a CO pressure of 50–100 atm. 2. The reactivity of methyl- and chlorine-substituted nitrobenzenes depends only slightly on the number and position of the substituents in the phenyl ring. 3. The reactivity of halogen-substituted nitrobenzenes diminishes in the order Cl > Br ≫ I.

The effect of pyridine bases and transition-metal oxides on the activity of PdCl2 in the carbonylation of aromatic mononitro compounds by carbon monoxide

Palladium chloride which is a catalyst for the preparation of phenylisocyanates by the carbonylation of nitro compounds is promoted by pyridine and its homologs and also by transition-metal oxides, which provide for the conversion of nitro compounds into phenyl-, methylphenyl-, and chlorophenylisocyanates in 75–92% yield and 84–97% selectivity at 200°C and 50–100 atm CO.

Catalytic synthesis of aromatic monoisocyanates from nitro compounds and carbon monoxide

1. We have synthesized aromatic monoisocyanates in 78–90% yield by carbonylation of nitro compounds with carbon monoxide in the presence of a PdCl2 + pyridine + V2O5, V2O4, or MoO3 catalyst at 200°C and a CO pressure of 50–100 atm. 2. The reactivity of methyl- and chlorine-substituted nitrobenzenes depends only slightly on the number and position of the substituents in the phenyl ring. 3. The reactivity of halogen-substituted nitrobenzenes diminishes in the order Cl > Br ≫ I.