Co Selective Reduction Of Sulfur-containing Alkyl Aromatic Nitro Compounds

The reduction of nitroarenes to corresponding amines is such a kind of classical organic reaction that it was widely applied in industry. However, the existence of alkylthio group in the nitroarenes deactivates most catalysts and degrades the reaction selectivity for the target products. Here in this paper, the CO selective reduction of nitroarenes was firstly introduced to reduce the alkylthio nitroarenes.The CO selective reduction of 4-propylthio-2-nitroaniline catalyzed by Ru3(CO)12 complex with NEt3, TPP or thermoregulated phase transfer phosphine ligand PEO-DPPPA were studied. Under their optimal conditions, the conversions of the substrate are respectively 90%,83%and 70%, while the selectivity of the product up-reaches 98%. When Ru3(CO)12 / PEO-DPPPA was used for the reaction, it could be recovered in aqueous phase and recycled several times.Three procedures to prepare 4-propylthio-2-nitro-aniline, a key intermediate for Albendazole, were also investigated in the paper. The results shown that the procedure catalyzed by sodium hydroxide was the best as the conversion of the substrate under this condition out-rival others to be 95%.