Nitro compounds reduction with ammonium formate

Catalyzed reductions with ammonium formate proceed with retention of configuration, at least for the case of nitro compounds. Treatment of steroid derivative (12) with ammonium formate in methanolic solution and a catalytic amount of palladium on charcoal gave exclusively amino steroid (13), as shown in equation (13). A similar technique has been used to produce members of the ephedrine family. 

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]... 

Clemmensen-type reduction.1 Aromatic ketones can be reduced to the corresponding methylene compounds with ammonium formate on transfer hydrogenation in acetic acid catalyzed by 10% Pd/C. The reduction is usually complete in 10-30 minutes at 110°. Halo and nitro substituents can be reduced under these conditions, and a,p-unsaturated carbonyl groups are reduced to saturated carbonyl groups. 

Reduction The stable Ni(0) complex is a useful catalyst for reduction of carbonyl compounds (to alcohols), sulfonyl azides (to sulfonamides), imines and nitro compounds (to amines) with ammonium formate. 

Co -", Ni "", Cu -", and Zn ) [73], GR-Pd-CdS [76], and hierarchical CdS-ZnO-GR hybrids [108]. It is found that their photoactivities for reduction of nitro compounds to amino compounds with ammonium formate (HCOONH4) for hole scavenger in N2 atmosphere (Scheme 8.11) under visible light irradiation are all remarkably enhanced as compared to the blank semiconductors [73,100-102,106, 107]. It has been concluded that the selective reduction efficiency can be driven by appropriate introduction of GR into the matrix of pure semiconductor, which can boost the transfer and prolong the lifetime of the electrons photoexcited from the semiconductor due to the tighter connection between GR and the semiconductor, as well as the optimization of the atomic charge carrier transfer pathway across the interface between GR and the semiconductor. 

Hydrogen gas can be replaced by ammonium formate for the reduction of nitro compounds to amines. The ammonium formate method is efficient, and the rapid workup procedure by simple filtration makes it widely used for converting the N02 to the NH2.96 For example, a-nitro esters are reduced to cx-amino esters in excellent yields on treatment with HC02NH4 and Pd/C in methanol.96... 

Zinc in the presence of ammonium chloride reduces primary, secondary and tertiary aliphatic nitro compounds but yields of hydroxylamines are moderate and formation of coupling products is common. Zinc with or without ammonium chloride reduces aromatic nitro compounds (e.g. 75, equation 49) into hydroxylamines in moderate to good yield. However, it has been mentioned that the reaction is sensitive to the grade and quality of zinc dust (equation 50) and aromatic amines have been obtained as major products in zinc reduction reactions. ... 

Partial reduction of aromatic polynitro compounds leads to nitro amines. The most successful reagents are the alkali metal or ammonium sulfides in aqueous alcoholIn some instances, sodium bicarbonate combined with sodium sulfide gives better results because of the formation of sodium hydrosulfide, which is believed to be the main reducing agent. Also, aqueous methanol is preferred to aqueous ethanol. Nitro compounds that are sparingly soluble in alcohol solutions may be reduced by hydrogen sulfide in pyridine solution. ... 

The value of the catalytic transfer hydrogenation route is demonstrated by the selective, high yield and rapid reduction of nitro aliphatic compounds to their corresponding amine derivatives using anhydrous ammonium formate (equation 26). A wide variety of nitro compounds are reduced in the presence of other functional groups including acids, esters and nitriles. Furthermore, the method is stereospecific and proceeds with retention of configuration pure racemic syn-nitro alcohols (39a) and (39b) were converted to the 5yn-amino alcohols (40a) and (40b) and the axial nitrosteroid (41a) afforded the 63-amine (41b). 

Several modifications of this reduction involve formates and are effective for reduction of various functional groups. A mixture of formic acid and ethyl magnesium bromide was used to reduce decanal to decanol in 70% yield. Decanal was also reduced to decanol in 69% yield by using sodium formate in N-methyl-2-pyrrolidinone as a solvent. Functional groups other than carbonyl derivatives can be reduced under relatively mild conditions with formate derivatives. Ammonium formate, in the presence of palladium on carhon was used to reduce an azide to a primary amine.Aliphatic nitro compounds are also converted to an amine with this reagent. l°... 

Reduction of the nitro group in 70 with zinc in hot sodium hydroxide results in formation of pyrrolo[2,l-(f][l,2,5]benzotriazepine 71 by intramolecular coupling of the amino group with the newly formed nitroso group (Scheme 16). If the reduction is carried out under the less rigorous conditions of zinc in aqueous ammonium chloride the intermediate hydroxy compound is formed <96T10751>. 

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