Reported here is the reduction of aromatic nitro compounds using sodium borohydride and transition metal sulfides as catalysts. The reaction conditions were optimized using the reduction of nitrobenzene as a model reaction. The catalysts studied were iron sulfide (Fe3S4), copper sulfide (CuS), zinc sulfide (ZnS), cobalt sulfide (Co3S4), and nickel sulfide (NiS). The reductions were monitored using gas chromatography. Quantitative conversions were achieved using Co3S4 and NiS, representing a ten-fold increase in reactivity compared to the non-catalysed reaction. Fe3S4and ZnS caused no apparent effect on the reduction of nitrobenzene while the reduction using CuS showed a marginal increase. The reduction method was applied to several aryl-nitro derivatives containing electron-withdrawing and electron-releasing groups. The new protocol developed did not result in the reduction of esters, amides, or alkenes, suggesting high selectivity of the reaction. The reductions were successful using only 3 molar equivalents of sodium borohydride. The heterogeneous reduction allowed for a simple removal of the catalysts. This newly developed method represents a milder alternative for the effective conversion of nitro groups into amino groups.                                                                               

Synthesis of aromatic amines via heterogeneous reduction of nitrobenzene derivatives using sodium borohydride and transition metal sulfides

247th National Meeting (2014)

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