Alkylation of aromatic nitro compound

The reductive alkylation of aromatic nitro compounds using H +Pd/G in the presence of 40% aqueous formaldehyde gives directly dimethylamino derivatives in good yield (Tq. 6.43. ... 

Reductive alkylation of aromatic nitro compounds is possible. The reaction of nitrobenzene with allylic or benzyl hahdes in the presence of an excess of tin metal in methanol, leads to the A,A -diaUyl or dibenzyl aniline. A similar reaction occurs with nitrobenzene, allyl bromide, and indium metal in aq. acetonitrile. 

The reactions of Grignard reagents with nitroarenes has provoked considerable study by Bartoli and co-workers, who have developed this procedure as a method for the alkylation of aromatic nitro compounds. They have found that an excess of the Grignard is required, first, to form an adduct that adds a second mole of Grignard reagent to the aromatic ring [Eq. (12) 29,30]. 

Bartoli G, Bosco M, Baccolini G (1980) Conjugate addition of RMgX to nitroarenes. A very useful method of alkylation of aromatic nitro compounds. J Org Chem 45 522-524... 

Malone RJ, Merten HL. (1992) A comparative mass transfer study in reductive N-alkylation of aromatic nitro compounds. In Pascoe WL, editor. Catalysis of organic reactions. Marcel Dekker, Boca Raton, EL, USA. 

The conjugate addition of alkyl Grignard reagents is the key step in a useful method for the alkylation of aromatic nitro-compounds. Thus, treatment of... 

The alkylation of aromatic nitro compounds by carbanions having a leaving group at the nueleophilic center is called Vicarious Nucleophilic Substitution of Hydrogen (VNS) (Seheme 36.1). This reaction is one of the scarce general processes that result in the formal nucleophilic aromatic substitution of hydrogen. 

Notable examples of general synthetic procedures in Volume 47 include the synthesis of aromatic aldehydes (from dichloro-methyl methyl ether), aliphatic aldehydes (from alkyl halides and trimethylamine oxide and by oxidation of alcohols using dimethyl sulfoxide, dicyclohexylcarbodiimide, and pyridinum trifluoro-acetate the latter method is particularly useful since the conditions are so mild), carbethoxycycloalkanones (from sodium hydride, diethyl carbonate, and the cycloalkanone), m-dialkylbenzenes (from the />-isomer by isomerization with hydrogen fluoride and boron trifluoride), and the deamination of amines (by conversion to the nitrosoamide and thermolysis to the ester). Other general methods are represented by the synthesis of 1 J-difluoroolefins (from sodium chlorodifluoroacetate, triphenyl phosphine, and an aldehyde or ketone), the nitration of aromatic rings (with ni-tronium tetrafluoroborate), the reductive methylation of aromatic nitro compounds (with formaldehyde and hydrogen), the synthesis of dialkyl ketones (from carboxylic acids and iron powder), and the preparation of 1-substituted cyclopropanols (from the condensation of a 1,3-dichloro-2-propanol derivative and ethyl-... 

Hydrogenations of aromatic nitro compounds are important in industry. A nitro group can be easily introduced into a benzene ring and then hydrogenated to the amine. During the hydrogenation, a number of coupling and alkylation reactions are possible as depicted in Fig. 2.31. 

Reduction of aromatic nitro compounds in aprotic medium in the presence of acetic anhydride [138] or alkyl halides [139] leads in high yield to O.A-diacylated or dialkylated aryIhydroxylamines, respectively. 

Recently Bartoli and co-workers [85-87] have published a number of papers dedicated to the systematic study of the reaction of aromatic nitro compounds with Grignard reagent. They confirmed the nucleophilic character of the alkylation of the ring. They also found that under their experimental conditions the nitro group was reduced to the nitroso group (17) ... 

Benkeser and co-workers found that the reduction of aromatic nitro compounds by the lithium-amine reagent stops rather cleanly at the aromatic amine even though arylamines can be reduced by excess lithium in ethylamine to cycloh exene derivatives. This surprising finding is aecounted for as follows. Reduetion of the nitro group is attended with generation of alkyl amide ions, and as the concentration of these ions increases an equilibrium is established between the arylamine and the... 

Hydrogenation of aromatic nitro compounds to aromatic amines Hydrogenation of aldehydes and ketortes to alcohols Hydrogenation of atomic olehnic groups Hydrogenation of unsaturatcd nitriles to unsaturated amines Hydrogenation of diolefins artd alkynes to monoolehns Hydration of ethylene oxide alkylation of aromatics with olehns oxidation of alcohols to aldehydes Oxidation of ethylene to ethylene oxide Synthesis of HCN from NH, and CH4 Oxidation of CH3OH to HCHO... 

Alkaline hydrolysis of a variety of organic compounds nitration of chlorobenzene alkylation of benzene with straight-chain olefins reduction of aromatic nitro compounds to corresponding aromatic amines with aqueous NajS or Na2Sj. 

Numerous individual substances were detected only in Ru04 extracts e.g. di- to pentachlorinated benzenes, 4-chlorobenzoic acid and 2,4-dichlorobenzoic acid 24, hexachlorocyclohexanes (a-,P-,y- and 5-HCH) 22, a technical mixture obtained during the synthesis of lindane, and the plasticizers alkylsulfonic acid phenylesters 23. These plasticizers were recently identified in riverine sediments (Franke et al. 1998). Furthermore, nitro-substituted benzoic acid and alkylated phenols 24 were observed. The occurrence of aromatic nitro compounds as a result of the oxidation of anilines can be excluded due to the contemporary appearance of amino compounds, e.g. 4-aminobenzoic acid or N-ethylaniline. However, the origin as well as the emission pathway of these compounds is still unknown. 

Alkyl groups in the ortho- or para-position of aromatic nitro compounds are also nitrosated, in the -position. Thus o- and -nitroacetophenone oxime are obtained in 73.5% and 67% yield, respectively, by nitrosating the corresponding ethylnitrobenzene with tert-butyl nitrite (for its preparation see Coe and Doumani267) in the presence of sodium ter/-butoxide.213... 

This reaction can be traced back to the initial work of Cadogan for the preparation of car-bazole by the reductive cyclization of aromatic nitro compounds with triethyl phosphite. This reaction was then extended by Sundberg to the fornnation of indoles by the treatment of o-nitrostyrene with triethyl phosphite or the formation of indolines from the o-alkyl nitrobenzenes. Thus the formation of indole from the reduction of o-nitfostyrenes is referred to as the Cadogan-Sundberg indole synthesis." ... 

Haba, M. Hatachi, A. Oxidation of alkyl-snbstitnted aromatic nitro compounds by chromate. Jpn. Tokkyo Koho JP 49048420, 1974 Chem. Abstr. 1975, 83, 9523. 

Another situation is observed during UV photolysis of samples (Figure 4.3b). The induction period in the kinetics of gel formation assumes a peculiar mechanism of AR generation in these conditions. NO3 dissociation via reaction (Equation 4.30) is strongly depressed, and the main path of photo-transformation of nitrate radicals is their decomposition into NO and atomic oxygen. Thus, primary closely located macroradicals R formed in reactions (Equation 4.89) and (Equation 4.90) can recombine with NO. Similarly to nitroso compounds, nitro compormds can add alkyl radicals with the formation of a stable spin adduct. Such an eventuality was shown by ESR in an example of aromatic nitro compounds [60]. For PVP, the mechanism resulting in radical R is ... 

Salts of alkyl nitro compounds exist as ions in which there is extensive delocalisation and in which the C—N bond has considerable double bond character [71, 72]. The N—O bonds give antisymmetric and symmetric frequencies in the ranges 1315—1205 and 1175— 1040 cm" The bands are usually doubled due to crystal splitting [72]. The salts of aromatic nitro compounds have been less studied but Ezumi et al. [73] have given some data for nitrobenzene and nitropyridine which suggest that these absorb at rather higher frequencies. 

Primary Amines—Several new and improved methods for the preparation of aromatic primary amines have been described. " The catalytic reduction of aromatic nitro-compounds to amines with hydrazine hydrate in the presence of iron(iii) oxide hydroxide proceeds smoothly and in high yields. Nitroarenes (1) react with Grignard reagents in the presence of copper(i) iodide, and are alkylated selectively on the aromatic moiety, accompanied by reduction of the nitro-group to the amine (Scheme 1). Both aryl and alkyl azides are rapidly... 

Oxidation of side chains. Aromatic nitro compounds that contain a side chain (e.g., nitro derivatives of alkyl benzenes) may be oxidised to the corresponding acids either by alkahne potassium permanganate (Section IV,9, 6) or, preferably, with a sodium dichromate - sulphuric acid mixture in which medium the nitro compound is more soluble. 

Cyclohexanones may serve as precursors to aromatic amines in a reductive alkylation, the source of hydrogen being aromatization of the cyclohexanone (66). In a variation, an aromatic nitro compound acts as both an amine precursor and a hydrogen acceptor (64). 

The latter reagent also methylates certain heterocyclic compounds (e.g., quinoline) and certain fused aromatic compounds (e.g., anthracene, phenanthrene). The reactions with the sulfur carbanions are especially useful, since none of these substrates can be methylated by the Friedel-Crafts procedure (11-12). It has been reported that aromatic nitro compounds can also be alkylated, not only with methyl but with other alkyl and substituted alkyl groups as well, in ortho and para positions, by treatment with an alkyllithium compound (or, with lower yields, a Grignard reagent), followed by an oxidizing agent such as Bra or DDQ (P- 1511). 

Such cyclohexadienes are easily oxidizable to benzenes (often by atmospheric oxygen), so this reaction becomes a method of alkylating and arylating suitably substituted (usually hindered) aryl ketones. A similar reaction has been reported for aromatic nitro compounds where 1,3,5-trinitrobenzene reacts with excess methyl-magnesium halide to give 2,4,6-trinitro-l,3,5-trimethylcyclohexane. Both... 

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