Nickel boride aliphatic nitro compound reduction

RNOi- RNHi.1 Nickel boride catalyzes reductions of aliphatic nitro compounds by NaBH4. Ni2B alone is ineffective. Reduction with NaBH4-NiCl2 in aqueous 2-propanol is much slower and results in more by-products. 

Titanium(II) reagents have also been used to reduce aliphatic nitro compounds to amines halo, cyano and ester groups are not reduced. Sodium borohydride, in the presence of catalytic amounts of nickel(II) chloride, reduces a variety of aliphatic nitro compounds to amines. Nickel boride (Ni2B) is an active catalyst for reductions of primary, secondary and tertiary nitro aliphatic compounds to amines. The reduction of nitrocyclohexane (45) yields cyclohexylamine (47) as well as small amounts of dicyclohexylamine (49), the latter being formed via reaction of intermediates (46) and (48 equation 28). 

Other Reductions. Aromatic and aliphatic nitro compounds are not reduced to amines by NaBHa in the absence of an activator. The NaBH4-NiCl2 system (see Nickel Boride) is a good reagent combination for this reaction, being effective also... 

Procedures were proposed for the reduction of aromatic nitro groups to amines. Sodium dithionitei78 and a combination of sulfur and hydrazine on activated carboni79 are reported to provide anilines in good to excellent yields. From aliphatic nitro compounds (Eq. 66), primary amines could be obtained with "nickel boride", prepared from nickel chloride and sodium borohydride.i ... 

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