Nitromethane displacements

Ozonolysis of the alkene frees the carboxylic acid, which reacts with carbonyl diimidazole (GDI) n a nucleophilic substitution at the carbonyl group. The relatively stable imidazole anion is the ea ing group. The anion of nitromethane displaces the second imidazole anion and completes the uence. 

Simple ketones and esters are inert. On the other hand, nitroalkanes react smoothly in r-butyl alcohol as a solvent with butadiene, and their acidic hydrogens are displaced with the octadienyl group. From nitromethane, three products, 64, 65, and 66, are formed, accompanied by 3-substituted 1,7-octadiene as a minor product. Hydrogenation of 65 affords a fatty amine 67 which has a primary amino function at the center of the long linear chain[46,61]. 

This class was first reported in 1924 and was formed 62HC(17)l) by cyclization of a-bromo-/3-aryl-y-nitroketones. The direct synthesis by oxygenation of 2-isoxazolines has not been reported. To date only 3-substituted derivatives have been prepared. Aryl-nitromethanes react with nitrostilbene to form isoxazoline A-oxide by a nitrile ion displacement (Scheme 138) <62HC(17)1, 68TL3375). 

In cm empirical approach (Helferich modification) it has been demonstrated on many occasions that mercuric salts (cyanide or bromide usually) in polar solvents such as nitromethane or acetonitrile favour the formation of a-glucosides, conceivably because under these conditions the mechanism of the halide displacement is rmimolecular and the carbonium ion can be approached from either side o). 

Di-/erJ-butylthianthrene and 1,3,6,8-tetra-tert-butylthianthrene were obtained from the diaryl sulfides in moderate yields by reaction with c. H2SO4 in nitromethane (68CB2956). A modified diaryl disulfide approach was based on intramoleculeir free radical substitution an o-phenoxy- (95% yield) or o-phenylthio-substituent (40% yield) being displaced as a radical (75G841). 

Dimethylpyrimido[4,5-f]pyridazine-5,7-dione 23 and its derivatives undergo attack at both C-3 and C-4. Under conditions of kinetic control, addition occurs preferentially at the more electron-deficient C, whereas thermodynamic control conditions, or the use of bulkier nucleophiles, favor addition at the less hindered position 3. This duality is illustrated by the addition of Grignard and organolithium reagents to C of 3-chloro analogue 24 (Equation 9), whereas stabilized nucleophiles such as the anion of nitromethane add at C-3 (Scheme 10) <2000CHE975>. Displacement of the 3-chloride occurs also upon treatment of 24 with amines (Equation 10) <2000CHE1213>. 

The reactions of 0-naphthol and 4-methoxyphenol with acetyl, propionyl, butyryl, 0-chloropropionyl and chloracetyl chlorides in acetonitrile produce some striking kinetic results109. The behaviour of acetyl, propionyl and n-butyryl chlorides fit reasonably well into the pattern for acetyl chloride in nitromethane and acetyl bromide in acetonitrile. However, with chloracetyl chloride the mechanism is essentially a synchronous displacement of covalently bound chlorine by the phenol and this process is powerfully catalysed by added salt with bond breaking being kinetically dominant. When no added salt is present the rate of hydrolysis of chloracetyl chloride is ca. 8000 times slower than that of acetyl chloride. Although, normally, in second-order acylation reactions, substituents with the greatest electron demand have been found to have the fastest rates, the reverse is true in this system. Satchell proposes that a route such as... 

When the reactions are carried out using nitric acid acetic anhydride in nitromethane the tetrasubstituted pyrroles are produced in poor yields, (7-11%) and products in which the acetyl group is displaced by the nitro group are also obtained (20-25%) yield [81 JCS(P1)1 ] (Fig. 1). 

Even for barriers as high as 3.5kcal/mol, when 0 — 200 cm"1, (2) — 0.2 rad, so that zero-point linear displacements of H atoms are 0.20-0.22 A. Thus, the torsion vibrations, unlike stretching modes, are really motions with wide amplitudes in the full sense of these words. The temperature dependence of can be found in the harmonic approximation using (2.82) experimentally, it can be extracted from the temperature dependence of the width of INS peaks assigned to torsion vibrations. As a typical example of this dependence, the results of Trevino et al. [1980] for deuterated nitromethane crystal are represented in Figure 7.8. 

The use of numerous polymer-supported optically active phase transfer catalysts was further extended by Kelly and Sherrington11351 in a range of phase transfer reactions including a variety of displacement reactions, such as sodium borohydride reductions of prochiral ketones, epoxidation of chalcone, addition of nitromethane to chalcone and the addition of thiophenol to cyclohexanone. Except in the chalcone epoxidation, all the examined resin catalysts proved to be very effective. However, with none of the chiral catalyst system examined was any significant ee achieved. The absence of chiral induction is a matter of debate, in particular over the possible reversibility of a step and the minimal interaction within an ion pair capable of acting as chiral entities in the transition state and/or the possible degradation of catalysts and leaching. 

The nitroalkane anion cannot undergo a direct two-electron oxidation. However, once the nitroalkane N(5)-adduct is formed the internal displacement of the stable N02 species (Equation 26) should be favorable energetically. The imine species formed on loss of N02 from the condensation product of nitromethane and Flox is the same... 

Another aspect of the formation of compounds and its influence on electrolytic dissociation is seen in connection with substituted ammonium salts of the type R3NHX although they are strong electrolytes in hy-droxylic solvents, c.g., in water and alcohols, they are dissociated to only a small extent in nitrobenzene, nitromethane, acetone and acetonitrile. It appears that in the salts under consideration the hydrogen atom can act as a link between the nitrogen atom and the acid radical X, so that the molecule RsN-H-X exists in acid solution. If the solvent S is of such a nature, however, that its molecules tend to form strong hydrogen bonds, it can displace the X ions, thus... 

Nitromethane by the Kolbe method (1872). In this method the chlorine atom of sodium chloroacetate is displaced by the nitro group, and the solution heated gently to effect decarboxylation. ... 

In summary, it can be said that, in homogeneous alkaline solution, either methanolic or aqueous, an equilibrium is established between the aldose, nitromethane, and deoxynitroalditols, and that, for successful addition, this equilibrium must be displaced in favor of the alditols, either through precipitation of their sodium salts from methanolic solution, or by direct crystallization from aqueous solution. Because of these requirements, the method is not so widely applicable as the cyanohydrin synthesis, but, for selected sugars, such as n-gZgcero-D-ZaZo-heptose and o-erythro-i -manno-octose, its simplicity and the satisfactory yields obtained make it the method of choice. 

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