Chemoselective Hydrogenation of Nitroarenes Catalyzed by Molybdenum Sulphide Clusters

Article abstract of DOI:10.1002/cctc.201601496

Herein, we describe an atom efficient and general protocol for the chemoselective hydrogenation of nitroarenes to anilines catalyzed by well-defined diimino and diamino cubane-type Mo₃S₄ clusters. The novel diimino [Mo₃S₄Cl₃(dnbpy)₃]⁺ ([5]⁺) (dnbpy=4,4′-dinonyl-2,2′-dipyridyl, L1) trinuclear complex was synthesized in high yields by simple ligand substitution reactions starting from the thiourea (tu) [Mo₃S₄(tu)₈(H₂O)]Cl₄?4 H₂O (3) precursor. This strategy has also been successfully adapted for the isolation of the diamino [Mo₃S₄Cl₃(dmen)₃](BF₄) ([6](BF₄)), (dmen=N,N′-dimethylethylenediamine) salt. Applying these catalysts, high selectivity in the hydrogenation of functionalized nitroarenes has been accomplished. Over thirty anilines bearing synthetically functional groups have been synthesized in 70 to 99 % yield. Notably, the integrity of the cluster core is preserved during catalysis. Based on kinetic studies on the hydrogenation of nitrobenzene and other potential reaction intermediates, the direct reduction to aniline is the preferential route.