Nitro groups, reduction amines

Reduction of nitro groups to amines may occur under either aerobic or anaerobic conditions ... 

Reduction reactions mediated by microorganisms may include the reduction of nitro bonds, sulfoxide reduction, and reductive dehalogenation. Reduction of the nitro group to amine involves the intermediate formation of nitrase and hydroxy amino groups. Selected reductive reactions may involve the saturation of double bonds, reduction of aldehydes to alcohols or ketones to secondary alcohols, or of certain metals. The main reductive processes in the subsurface environment have been discussed earlier in this chapter. 

Fusion of the imidazole ring to pyrrolo-benzothiadiazepine 340 can be achieved by straightforward TosMIC cycloaddition approach (Scheme 72, Section 4.2 (1994JHC1033)). An alternative sequence starts with the addition of nitromethane to the C-N double bond on the thiadiazepine ring, nitro group reduction and manganese oxide oxidation of the intermediate dihydroimidazole derived from amine 342 and tiiethyl ortho formate. 

Titanous ions are known to reduce nitro groups to amines and also other kinds of N—O bonds to N—H. Reduction of the cyclic hydroxylamine de-... 

The resin-bound perfluoroalkylsulfonyl linker is compatible with many common solid-phase reactions, such as tin dichloride-mediated aromatic nitro group reduction, trifluoroacetic acid-mediated tBoc deprotection, reductive amination reactions, acylation, and sulfonation. It is possible to perform several sequential synthetic reactions on the nonflate resin so that multistep syntheses can be carried out. The solid-phase approach provides an operationally simple, inexpensive, and general protocol for the cleavage... 

The synthesis of the tetracyclic intermediate 49 was therefore studied in the hope that it might further cyclize to the desired lycorine skeleton. Birch reduction of o,p-dimethoxyphenethylamine led to the amine 50 which was converted into 51, giving rise in turn upon hydrolysis to 49. Its structure rests on physical data. Ordinary methods for nitro group reduction seemed to also destroy the 289-nm chromophore, but hydrogen transfer (a-phellandrene and Pd/C) gave a product which analyzed for the product of nitro reduction to amine in 49, the mass spectrometric data also being in agreement. The product was, however, not affected by diazotization, and, on the basis of spectral data, was... 

Aqueous reductions are useful for amine synthesis. Organic reducing agents (N H or formic acid) reduce amides or imines . Active metals in acid reduce nitro groups . Reduction of Ph3PNBr with I ... 

The synthetic potential of reductions by formate has been extended considerably by the use of ammonium formate with transition metal catalysts like palladium and rhodium. This forms a safe alternative to use of hydrogen. In this fashion it is possible to reduce hydrazones to hydrazines, azides and nitro groups to amines, to dehalogenate chloro-substituted aromatics, and to carry out various reductive removals of functional groups. For example, phenol triflates are selectively deoxygenated to the aromatic derivatives using triethylammonium formate as reductant and a palladium catalyst. - These recent af li-cations have been reviewed. 

The predominant metabolic pathway appears to be hydroxylation of alkyl groups or N-dealkylation. To a lesser extent, a cyclized compound, benzimidazole, and the reduction products of nitro groups or amines, are also possible metabolic products. 

Figure 13.1 Covalent attachment of an enzyme to derivatized polypyrrole (a) polypyrrole polymer (b) nitration of polypyrrole (c) electrochemical reduction of nitro groups to amine groups (d) attachment of enzyme to amine groups with carbodiimide [32],...

Microbial reduction of toxic organics is carried out by reduction enzymes. Major reduction reactions of selected toxic organics are shown in Table 13.5. The reduction of the nitro group to amine involves the formation of a nitro and a hydroxyamino group. This type of reduction reaction occurs during the microbial metabolism of various pesticides. Organophosphorous pesticides such as para-thion, paraoxon, or fenitrothion are often reduced to nontoxic amino compounds (Miyamoto et al., 1966 Matsumura and Benezet, 1978). 

Amathamides A (108) and B (109) were synthesized by Osuna et al. from 3-hydroxybenzaldehyde 120 and it is depicted in Scheme 10 [58], In the synthetic sequence, aldehyde 120 was converted into required dibromomethoxybenzaldehyde 121 via bromination followed by methylation. Then aldehyde 121 was converted into amine 123 on nitroolefination followed by Michael addition and nitro group reduction (Scheme 10) [58], Amine 123 was coupled with A-methyl-L-proline to get amide 124. 

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 ... 

With aromatic compounds which are very reactive towards electrophiles, it may be preferable to introduce a nitroso or arylazo group rather than a nitro group reduction to the amine can be effected in a number of ways (reaction 91)... 

Grafting is performed on graphene by reduction of 4-nitrophenyldiazonium cations and nitro groups to amines. Activation using GA... 

De Groot s dendrons (Scheme 15) were constructed with a nitro fimctional-ity as the trigger (activation is achieved upon reduction of the nitro group to amine) and the anticancer drug taxol as the reporter imits. The nitro fimc-tion in dendrons 22 and 23 was then reduced under mild conditions (Zn, acetic add). Analysis by thin-layer chromatography indicated complete disappearance of the starting material and formation of free taxoL NMR spectroscopic studies also confirmed the complete release of the taxol molecules. However, there is no data yet to prove that taxol dendrons can be activated under physiological conditions. 

Full details have been published on the reduction of imines to optically active amines with chiral borohydride reagents. The homogeneous hydrogenation of azo-, imino-, and nitro-groups to amine derivatives is reported a rhodium salt-sodium borohydride system is used. 

Quinn et al. (2010) carried out reduction of heteroaromatic and aromatic nitro groups to amines using Pd/C or Pt/C catalyst, which is extremely effective with 1,4-cyclo-hexadiene as the hydrogen transfer source. In general, the reactions were completed... 

Carbonyl Compounds Multiple Bond Reduction Nitrile Group Nitro Compounds Reductive Amination Wolff-Kishner Reduction... 

It is convenient to include under Aromatic Amines the preparation of m-nitroaniline as an example of the selective reduction of one group in a polynitro compound. When wt-dinitrobenzene is allowed to react with sodium polysulphide (or ammonium sulphide) solution, only one of the nitro groups is reduced and m-nitroanUine results. Some sulphur separates, but the main reaction is represented by ... 

---