Nitro anions

Many mtrogen-contammg functional groups react with fluorine to give a variety of products Several reagents add fluorine to nitro anions, as shown in equations 7 and 8 66, 67, 68] A detailed review of these reactions was recently published [69]... 

The alkylation of enamines with nitroolefins, which gives intermediates for reductive cyclization (6S2), also provided an example of a stable cycliza-tion product derived from attack of the intermediate imonium function by the nitro anion (683). A previously claimed tetrasubstituted enamine, which was obtained from addition of a vinylsulfone to morpholinocyclohexene (314), was shown to be the corresponding cyclobutane (684). Perfluoro-olefins also gave alkylation products with enamines (685). Reactions of enamines with diazodicarboxylate (683,686) have been used diagnostically for 6-substituted cyclohexenamines. In a reaction of 2-penten-4-one with a substituted vinylogous amide, stereochemical direction was seen to depend on solvent polarity (687). 

The sequence (81 84) has been proposed - to account for this process which involves decomposition of the aci-nitro anion by strong acid. The a-carbonyl group presumably stabilizes the aci-salt and thus could be responsible for inhibiting the normal Nef reaction. A similar transformation has been observed in the case of a 16-nitro-17-0X0 steroid. 

Interesdng intramolecular cycllzadon of Tnitroalkyl radicals generated by one-electron oxidadon of nci-nitro anions vrith CAN is reported. As shown in Eq. 5.44, stereoselecdve formadon of 3,4-funcdonalized tetrahydroflrtans is observed. TNitro-6-heptenyl radicals generated by one electron oxidadon of aci-nitroanions vrith CAN afford 2,3,4-trisnbsdtuted tetrahydropyrans. The requisite nitro compounds are prepared by the Michael addidon of 3-buten-Tal to nitroalkenes. 

Nitro Anions Remov of a proton from an aliphatic nitro compound gives a carbanion (R2C-NO2) that can be alkylated at oxygen or carbon. ... 

The negative ClogP term shows that highly hydrophilic molecules for this data set would present better inhibitory activities against topo I. Two compounds (Ri = R3 = R4 = R5 = H, R2 = NO2 and Ri = R3 = R4 = R5 = H, R2 = F) in Table 4 for the development of QSAR Eq. 6 were deemed to be outliers on the basis of their deviation (>2s). The outlier (Ri = R3 = R4 = R5 = H, R2 = NO2) is much more active than expected, by three times the standard deviation. This may be due to the formation of nitro anion radicals that interact with DNA [48]. The other derivative (Ri = R3 = R4 = R5 = H, R2 = F) is... 

The acidity of the unadivated cubyl-H is comparable to NH3 (pKa 38). Cubyl H-atoms are at least 105-106 times more acidic than vinyl and phenyl hydrogens (K. A. Lukin, J. Li, P. E. Eaton, N. Kanomata, J. Hain, E. Pun-zalan, R. Gilardi, Synthesis and chemistry of 1,35,7-tetranitrocubane induding measurement of its acidity, formation of o-nitro anions, and the first preparations of pentanitrocubane and hexanitrocubane , J. Am Chem. Soc, 1997,119, 9591-9602 and the references cited therein). 

Recently, time-resolved resonance Raman spectroscopic studies47 of the excitation of 2-(2, 4 -dinitrobenzyl)-pyridine 58 and 4-(2, 4 -dinitrobenzyl)pyridine have shown that three transient intermediates are involved they are aci-nitro acid 59, aci-nitro anion 60 and N—H... 

A number of 5-nitro-2-furaldehyde derivatives, called nitrofurans, are used in the treatment and/or prophylaxis of microbial infections, primarily in the urinary tract. Recent evidence suggests that the reduction of the 5-nitro group to the nitro anion results in bacterial toxicity. Intermediate metabolites modify various bacterial macromolecules that affect a variety of biochemical processes (e.g., DNA and RNA synthesis, protein synthesis) this observation may explain the lack of resistance development to these drugs. Evidence also indicates that the nitro anion undergoes recycling with the production of superoxide and other toxic oxygen compounds. It is presumed that the nitrofurans are selectively toxic to microbial cells because in humans, the slower reduction by mammalian cells prevents high serum concentrations. 

Nifurtimox (Lampit) is a nitrofuran derivative whose likely mechanism of action for kUhng of trypanosomes is through the production of activated forms of oxygen. Nifurtimox is reduced to the nitro anion radical, which reacts with oxygen to produce superoxide and hydrogen peroxide. The free radical metabolites, an absence of parasite catalase, and a peroxide dehciency lead to hpid peroxidation and cell damage. This production of activated oxygen results in toxicity to the protozoal cells. 

Fig. 6 Scheme of futile cycling of metronidazole in the presence of oxygen. Nitro anion radicals are converted back to the inactive reoxidized form. By-products of this conversion are superoxide radicals... 

The acidity of 1,3,5,7-tetranitrocubane, which features nitro groups on alternate comers of cubane, has been measured (p/C, 21) and reactions of the corresponding o-nitro anion have been explored.183... 

As shown by means of electrochemical ESR spectroscopic methods and confirmed by ab initio calculations (Alberti et al. 1995), the first electron is accommodated in the more accessible nitrobenzopyran moiety. Next, the second electron fits into the nitroindoline moiety in virtually the same orbital that in the anion radical of mon<9-nitro-spiro(indoline-benzopyran), is occupied by the unpaired electron. The mono-nitro anion radical is also formed by the aforementioned reaction with terf-BuOK in DMSO, Scheme 1-63. 

In the initially proposed mechanism, the intermediate 2-nitro-2-propyl radicals, Me2(N02)C, undergo two reactions with the more basic (nucleophilic) thiolates addition of thiolates leading to SRN1 products (Equation 10.20 in Scheme 10.32), and SET to yield the nitro anion and thiyl radicals (RS ), Equation 10.21, which combine to give disulfide. 

A correlation of the pAT-values of nitrobenzene anions with the substituent constants o has also been reported (Griinbein et al., 1969). Figure 2 shows this type of correlation for the nitro-anions... 

The definition also includes species in which a common radical function such as a ketyl, nitro anion-radical, or semiquinone is conjugated with a heteroaromatic system, e.g., 6-9. Certain major radical series are, however,... 

The ion-pairs of nitropyridines continue to attract attention. Consistent with the substituent s being the primary residence for spin and charge in nitro anion-radicals, it was found that the counterion is associated with the oxygen atoms of the nitro group and lies on the C2 axis of the radical.80... 

The initially formed chlorides PyX ionize to a pyridinium halide while PyR represents mixed 1,4- and 1,2-dihydropyridines.233,234 4-Nitrobenzyl halides react by a different mechanism the initial step here is electron transfer from 66 to the halide to give a nitro anion-radical which subsequently loses halide. Since this reaction involves ionic intermediates it is much more susceptible to solvent effects than the atom transfer reaction.235,236... 

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