Sodium dithionite reduction of nitroarenes using viologen as an electron phase-transfer catalyst

Organocatalytic Reduction of Nitroarenes with Phenyl(2‐quinolyl)methanol

“…Moreover, in the last decades, the focus on green and sustainable methodologies, also associated to the progress of organocatalysis, [7] stimulated the study of metal-free processes. In this context, a great variety of non-metal and transition metal free reagents were exploited for the reduction of nitro aromatics to anilines such as 9,10-dihydroanthracene, [8] 1,4-dihydropyridine systems, [9] elemental sulfur, [10] thiols, [11] Baker's Yeast in basic solution, [12] fullerene/H 2 , [13] glucose, [14] vasicine, [15] trichlorosilane/NR 3 , [16] triethylsilane/B(C 6 F 5 ) 3 , [17] diboron compounds, [18] viologen/Na 2 S 2 O 4 , [19] N,N'-bis(trimethylsilyl)-4,4'bipyridinylidene, [20] 2-aminoquinazolin-4(3H)-one/N 2 H 4 , [21] char-coal/NaBH 4 in aqueous medium, [22] as well as different carbonbased catalysts in the presence of N 2 H 4 , [23] NaBH 4 , [24] isopropanol, [25] or subcritical water [26] as hydrogen sources, and even the system isopropanol/KOH. [27] Recent studies from our laboratory showed the possibility to apply pyridylmethanols as hydrogen donors, mimetic of Hantzsch ester (HEH), for metal free reductions of aromatic/ heteroaromatic nitro compounds to the corresponding amines.…”

Microwave‐assisted reduction of aromatic nitro compounds with novel oxo‐rhenium complexes

“…[59,62,63] Comparing our results with those of the groups that reduced nitrobenzene with methods that do not include a metal as a catalyst or as a reducing agent, we can see that the yields are similar but still the excess of the reducing agent that they employed would be still problematic for large scale processes. [16,64,65] The organometallic catalysts containing a N-heterocyclic carbene that we considered perform as good as our systems, but they require milder condition than ours. [48,53,66] An interesting solution is the one offered by Sobhani et al, [66] which realized a catalyst (Pd-NHC-g-Fe 2 O 3 -nbutyl-SO 3 H) in which Pd is bound to an NHC anchored to a magnetic bead that is easy to recover thank to the use of an external magnetic field.…”

Mild and selective reduction of aldehydes utilising sodium dithionite under flow conditions

“…Sodium dithionite can act as a powerful reducing agent [ 16 ], is mild, easy to use, and it is compatible with protic solvents like water and isopropanol. It has previously been used to reduce a range of different organic functional groups including aldehydes and ketones [ 17 – 18 ], pyridinium ions to afford piperidines [ 17 ], benzil groups [ 19 ], nitroarenes and nitroalkanes in the presence of dialkyl viologen electron transfer catalysts [ 20 – 21 ] and immobilized nitroarene’s under phase transfer conditions [ 22 – 23 ].…”