Nitro groups, aliphatic partial

Formic acid is a good reducing agent in the presence of Pd on carbon as a catalyst. Aromatic nitro compounds are reduced to aniline with formic acid[100]. Selective reduction of one nitro group in 2,4-dinitrotoluene (112) with triethylammonium formate is possible[101]. o-Nitroacetophenone (113) is first reduced to o-aminoacetophenone, then to o-ethylaniline when an excess of formate is used[102]. Ammonium and potassium formate are also used for the reduction of aliphatic and aromatic nitro compounds. Pd on carbon is a good catalyst[103,104]. NaBH4 is also used for the Pd-catalyzed reduction of nitro compounds 105]. However, the ,/)-unsaturated nitroalkene 114 is partially reduced to the oxime 115 with ammonium formate[106]... 

Nitro Compounds. Under mild conditions, aromatic nitro compounds are hydrogenated easily to amines.518 The reaction may give partially reduced products, according to the circumstances. Palladium, platinum, and nickel are used frequently for this reaction. For example, nitro and benzyl ester functions are reduced on Pd(OH)2/C on THF and on Pd/C in EtOH.519 Aliphatic nitro groups are reduced more slowly. 

Subsequently, with the newly developed sterically bulky chiral triazolium salt precatalyst, the Rovis group disclosed a homoenolate Michael addition reaction of enals to nitroalkenes that delivers complementary syw stereoselectivity and allows coupling with aliphatic nitroalkenes. Bulky substituents in the ortho ortho position of the Al-aryl ring of the NHC are crucial for the success of this reaction as it would shift product distribution toward the desired nitro ester by partially bloeking the aeyl anion position (Scheme 7.64). 

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