Efficient reduction of nitroarenes using supercritical alcohols as a source of hydrogen in flow-type reactor in the presence of alumina

Reduction of nitroarenes using supercritical alcohols as a source of hydrogen was studied in a flow reactor in the presence of alumina at temperatures 515–615 K and residence times not exceeding 6 min. In the reaction of nitrobenzene reduction by 4-methylpentan-2-ol in supercritical (sc) CO2, the selectivity for aniline reached 95% with a conversion of 71%. If methanol was used as the reducing agent, the main reaction product was N,N-dimethylaniline. It was shown that the use of scCO2 co-solvent had a significant impact on the course of the reduction process including secondary and side reactions. The conditions for the reduction of halogenated nitroarenes into respective amines with high conversion and nearly 100% selectivity almost without dehalogenation were found.