Recent Developments in Heterogeneous Selective Hydrogenation of Halogenated Nitroaromatic Compounds to Halogenated Anilines

Polymer supported palladium nanocrystals as efficient and recyclable catalyst for the reduction of nitroarenes to anilines under mild conditions in water

“…Interestingly, by carrying out the nitrobenzene hydrogenation using H 2 (1 atm) as reducing agent instead of NaBH 4 , the reaction reached completion after 6 h (entry 16), revealing that Pd-pol catalytic system was more active using NaBH 4 .…”

“…In order to overcome all these disadvantages, great efforts have been made by the scientific community with the aim to develop greener and cheaper hydrogenation catalytic systems with higher yields. Numerous protocols for the reduction of aromatic nitro compounds have been reported in the literature [2][3][4][5][6][7]. They include: 1) hydrogenation under H 2 at various pressures promoted by various catalysts [8], such as Pt/C [9], Rh 3 Ni 1 [10], Pd/C [11][12][13], Pd [14,15] and Rh [16] nanoparticles; 2) catalytic reduction in the presence of CO and H 2 O [17] and photocatalytic hydrogenation [18]; 3) catalytic transfer hydrogenation promoted, for example, by Cu [19], Pd [20], palladium/graphene [21], Au [22], Ru [23] or Fe 3 O 4 -Ni [24] nanoparticles with reducing agents other than molecular hydrogen [25,26], including hydrazine [27][28][29][30][31][32], silanes [33,34] and sodium borohydride [35][36][37][38][39][40][41].…”

Heterogeneous Catalysis on Nanostructured Carbon Material Supported Catalysts

“…122,123 The hydrogenation of simple aromatic nitroarenes (see section 7.2.2.3) poses few problems and is carried out catalytically on very large scales. When other reducible groups are present in the same molecule, it is often difficult to catalytically reduce the nitro group in a selective manner.…”

Carbon supported gold and silver: Application in the gas phase hydrogenation of m -dinitrobenzene

“…Exclusive -NO 2 group reduction is difficult to achieve in the presence of other reactive functionalities such as carbonyl, cyano, alkenyl or halogen groups [2]. The focus has moved from conventional Fe promoted reduction in acid media (Béchamp process) [3] to the application of transition metal (e.g. Pd [4], Pt [5]) catalysts.…”

“…Surface oxygen-containing functionalities (i) act as metal-anchoring sites [22], (ii) promote reduction of the metal precursor [23] and (iii) lower hydrophobicity and improve support accessibility during catalyst synthesis [10]. The concentration and nature of surface groups can be tailored by treatment with oxidising agents (HNO 3 [24].…”