Nitro compounds Nitromethane

Nitro compounds. Nitromethane Nitrobenzene ni-Dinitrobenzene. Amides and imides. Acetamide re-Caproamide Acetanilide Benz-anilide Phthalimide. 

The PE spectra of the two basic organic nitro compounds, nitromethane and nitrobenzene, were first analysed by Rabalais139. These and other nitro compounds have been the... 

Among aliphatic nitro compounds nitromethane was only recently recognized as an explosive. Tetranitromethane is not explosive but can form an explosive when mixed with combustible substances. Tetranitromethane possesses here a chMacter... 

The largest group of organic molecular compounds, in which hydrogen bond formation plays no part, are the compounds, usually in the ratio 1 1, between on the one hand aliphatic and aromatic nitro compounds (nitromethane, tetranitro-methane, chloropicrin CC13N02, nitrobenzene, s-trinitrobenzene, picric acid), quinones, anhydrides (phthalic acid-and maleic acid anhydride) and ketones with on the other hand especially aliphatic and aromatic amines (aniline, pyridine), unsaturated aliphatic and aromatic hydrocarbons, ethers etc. 

The simplest of the nitro compounds, nitromethane H3CNO2, is an oily liquid that causes anorexia, diarrhea, nausea, and vomiting, and damages the kidneys and... 

Allylic nitro compounds are obtained by the reacdon of cyclic ketones with nitromethane in the presence of 1,2-diaminoethane fl mol% as catalyst. Because exa-cyclic nitroalkenes are rearranged to the fi)iifo-cyclic fi,Y-nitroalkenes, allylic nitro compounds are selecdvely produced fEq. 3.21. ... 

Recently, elegant synthesis of ruin -MRS carbapenum has been reported. Sequential reaction of nitromethane via conjugate addition-elimination to a,fi-unsanirated esters followed by Pd-catalyzed subsdnidon of the residdng allyl nitro compound with the naphthosultam affords the allyladon product which is an and fEq. 7.20. ... 

Nitrating propane produces a complex mixture of nitro compounds ranging from nitromethane to nitropropanes. The presence of lower nitroparaffins is attributed to carbon-carbon bond fission occurring at the temperature used. Temperatures and pressures are in the range of 390°-440°C and 100-125 psig, respectively. Increasing the mole ratio of propane to nitric acid increases the yield of nitropropanes. Typical product composition for 25 1 propane/acid ratio is ... 

Nitromethane has been used as a solvent for molecular bromination297. The bromination of polymethylbenzenes in nitromethane, acetic acid, and 1 1 mixtures of these solvents at 30 °C, showed that rates were much faster (about 330-fold) in nitromethane than in acetic acid. With nitromethane, in the bromine concentration range 0.01-0.02 M, the reaction was third-order in bromine. The relative deactivating effects of m-halogen substituents were measured in terms of the time taken for 10 % reaction to occur, and these values are given in Table 71 from which the relative reactivities in the different solvents are apparent the deactivating effects of the m-nitro substituent were obtained by comparison with the reactivity of chloromesitylene at different concentrations (0.035, 0.055 M) of reactants. The results for the nitro compounds were interpreted in the same way... 

The condensation of nitro compounds and imines, the so-called aza-Henry or nitro-Mannich reaction, has recently emerged as a powerful tool for the enantioselective synthesis of 1,2-diamines through the intermediate /3-amino nitro compounds. The method is based on the addition of a nitronate ion (a-nitro carbanion), generated from nitroalkanes, to an imine. The addition of a nitronate ion to an imine is thermodynamically disfavored, so that the presence of a protic species or a Lewis acid is required, to activate the imine and/or to quench the adduct. The acidic medium is compatible with the existence of the nitronate anion, as acetic acid and nitromethane have comparable acidities. Moreover, the products are often unstable, either for the reversibility of the addition or for the possible /3-elimination of the nitro group, and the crude products are generally reduced, avoiding purification to give the desired 1,2-diamines. Hence, the nitronate ion is an equivalent of an a-amino carbanion. 

The condensation of arylsulfonyl acetonitriles 369a-c with 22a proceeds via addition of the in-situ formed anion 370 to the arylsulfonyl acetonitriles 369 to afford the dimers 371, in 69-94% yield, and hexamethyldisiloxane 7 [136]. Furthermore, y9-dicarbonyl compounds such as ethyl acetoacetate 372 a or ethyl benzoyl-acetate 372b are O-silylated by 22 a or 22 c to rather stable alkyl 3-O-trimethylsilyl-oxycrotonoate 373a and alkyl 3-0-trimethylsilyloxy-3-phenyl acrylate 373b [130]. Aliphatic nitro compounds such as nitromethane are O-trimethylsilylated and further transformed into oligomers [132] (cf Section 7.6) and are thus unsuitable reactants for silylation-C-substitutions (Scheme 4.50). 

Many of the compounds that undergo ready base-catalysed keto i enol prototropic changes, e.g. / -keto esters, l,3-(/ -) diketones, aliphatic nitro compounds, etc., form relatively stable carbanions, e.g. (25), that can often be isolated. Thus it is possible to obtain carbanions from the keto forms of the /J-keto ester (23a) and nitromethane (24a) and, under suitable conditions, to protonate them so as to obtain the pure enol forms (23b) and (24i>), respectively. It thus seems extremely probable that their interconversion follows the intermolecular pathway (a). The more acidic the substrate, i.e. the more stable the carbanion to which it gives rise, the greater the chance that prototropic interconversion will involve the carbanion as an intermediate. 

See Nitromethane Carbon disulfide See other C-NITRO COMPOUNDS... 

The base-catalyzed reaction of nitromethane with a-amidoatkyl sulfones gives the nitro compounds as in Eq. 4.117 the nitromethyl group is converted into a carboxylic group to give a-amino acids by the Nef reaction using KMn04.155... 

The reactivity of carbon is much enhanced by the double deprotonated intermediates of nitro compounds. Except for nitromethane, other nitroalkanes are alkylated to give the C-alkylated products in 50-60% yield by this procedure (see Eq. 5.4).9 10... 

Couplings of nitroalkyl radicals with nucleophiles such as CN-, N, N02, and other nitrogen nucleophiles provides a useful method for the preparation of nitro compounds with such groups at the a-position.49 65 The alkylation of nitromethane with trialkylborane is possible by electrolysis, in which alkyl radicals may be involved (Eq. 5.46).66... 

Asymmetric synthesis of tricyclic nitro ergoline synthon (up to 70% ee) is accomplished by intramolecular cyclization of nitro compound Pd(0)-catalyzed complexes with classical C2 symmetry diphosphanes.94 Palladium complexes of 4,5-dihydrooxazoles are better chiral ligands to promote asymmetric allylic alkylation than classical catalysts. For example, allylic substitution with nitromethane gives enantioselectivity exceeding 99% ee (Eq. 5.62).95 Phosphi-noxazolines can induce very high enatioselectivity in other transition metal-catalyzed reactions.96 Diastereo- and enantioselective allylation of substituted nitroalkanes has also been reported.9513... 

Bowman has surveyed the reactions of cx-substituted aliphatic nitro compounds with nucleophiles, which undergo either S l substitution or polar reaction (Scheme 5.16).118 The reactions between a wide variety of nucleophiles and BrCH2N02 are shown in Scheme 5.17.119a b All the thiolates, PhS02 and I attack Br to liberate the anion of nitromethane. The hard nucleophiles, MeO , OH, and BH4 attack the hard H+ electrophilic center. Phosphorous nucleophiles attackthe oxygen electrophilic center, and only Me2S attacks the carbon electrophilic center. 

The hydrogenation in the presence of Pd/C is also effective for the conversion of nitro compounds to amines.94 The Michael addition of nitromethane to 2-alkenoic esters followed by catalytic hydrogenation using 10% Pd/C in acetic acid and hydrolysis is a convenient method for the preparation of 3-alkyl-4-aminobutanoic acids, which are important y-amino acids for biological study (Eq. 6.48).94b The reduction can be carried out at room temperature and atmospheric pressure. 

The reaction of tertiary nitro compounds with the sodium salt of nitromethane followed by the Nef reaction provides a good method forthe preparation of quaternary aldehydes (Eq. 7.10).8 Because the nitromethyl group can be transformed into other groups such as CN, C02H, or CH2NH2, the SRN I reaction of tertiary nitro compounds with the anion of nitromethane is a synthetically useful method (Kornblum reaction).10 For example, the nitromethylation of tertiary nitro compounds has been applied for preparing starting materials for cascade polymers (Eq. 7.11).9... 

Experiment.—Dissolve 1 c.c. of nitromethane in water and test the solution with litmus paper. Then add some phenolphthalein and, drop by drop from a burette, OliV-sodium hydroxide solution. Before a permanent pink colour develops about 2 c.c. of the alkali will be added—a sign that an acid, aci-nitromethane, H2C NOOH, has been formed from the neutral nitromethane. A small sample of this solution gives with ferric chloride a blood-red colour, characteristic of aci-nitro-compounds. The salts of the oci-compound undergo extensive hydrolysis. This is shown by further addition of 0-1 N-alkali which produces a deep red colour. If 10 c.c. of alkali were added and 5 c.c. of 0-1 JV-hydrochloric acid are now run in the solution is decolorised because the liberated oci-compound restricts the hydrolysis of its salt. But the conversion of H2C N02H into H3C.N02 proceeds so rapidly that the red colour reappears in a few moments. 

It appears that gas-phase basicity of nitro compounds has been studied only scarcely. Thus, only the values of the parent compounds, nitromethane (179.2 kcalmol-1) and nitrobenzene (193.4 kcalmoD1), are found in the comprehensive listing given in Reference 39. The rather high PA values for nitro compounds suggest protonation by common chemical ionization reagent systems, such as hydrogen (H3+) and methane (CH5+). 

As in the case of other groups which activate adjacent CH6, the nitro group in aliphatic nitro compounds soon acquired importance in preparative organic chemistry, particularly for condensation reactions. The condensing agents are normally bases. Thus nitromethane will react with benzaldehyde to give first a nitro-alcohol and then a nitro-olefin (Priebs, 188425) ... 

It will be helpful at this point to review a few well-known features of the electrochemical behavior of nitro and nitroso compounds. The reader is referred to a previous review in this series for more detail on this point1. The primary fact of which one must be aware of is that the electrochemistry of nitro compounds is exclusively cathodic the high oxidation level of nitrogen in the nitro group means that while they are easily reduced, they generally cannot be oxidized. As a matter of fact, nitrobenzene and nitromethane have been used as solvents for electrochemical oxidations because of their stability under anodic conditions2. Nitroso compounds are readily both oxidized and reduced, although the literature on these substances is much more sparse. 

Secondary nitro compounds can be converted into carbanions in similar fashion. Interesting highly functionalized adducts (46) were prepared by addition to levoglucosene (45) (equation 17)59. Mixtures of diastereomeric adducts were generally formed60. The adduct from nitromethane undergoes double Michael addition followed by aldol condensation to afford the novel adduct 47. 

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