Esters, nitrate, from alkyl

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-... 

Acetone cyanohydrin nitrate, a reagent prepared from the nitration of acetone cyanohydrin with acetic anhydride-nitric acid, has been used for the alkaline nitration of alkyl-substituted malonate esters. In these reactions sodium hydride is used to form the carbanions of the malonate esters, which on reaction with acetone cyanohydrin nitrate form the corresponding nitromalonates. The use of a 100 % excess of sodium hydride in these reactions causes the nitromalonates to decompose by decarboxylation to the corresponding a-nitroesters. Alkyl-substituted acetoacetic acid esters behave in a similar way and have been used to synthesize a-nitroesters. Yields of a-nitroesters from both methods average 50-55 %. 

In contrast to the carboxylic esters, no transesterification or desulfonation (cleavage of the C-S bond) is observed, in the alkyl nitration of alkyl sulfonate esters. Ethyl butanesulfonate is converted to ethyl a-nitrobutanesulfonate (54%) and the potassium salt of o-nitrobutanesulfonic acid (11%), about 33% of the ester being recovered (eq 15). The salt of a -nitrobutanesulfonic acid arises from a B-elimination with the loss of ethylene (13). 

Both protic- or Lewis-acid-catalyzed nitration of aromatics can be carried out with a/ky/ nitrates (i.e., alkyl esters of nitric acid). Acid catalysts are assumed to form nitronium ion from alkyl nitrates or strongly polarized complexes. 

The rate data for reaction of NO3 with aliphatic esters show that the presence of the ester group in an organic molecule has little influence on the reactivity compared to the parent alkane. The reactivity trends exhibited by the nitrate radical for reactions with alcohols, ethers and esters are similar to those shown for the analogous reactions of hydroxyl radicals. The major products identified from the NO3 radical-initiated oxidation of alcohols, ethers and esters under atmospheric conditions were esters, carbonyls and alkyl nitrates. Similar products arise from the reactions of OH radicals with these molecules under atmospheric conditions. 

Cationic, anionic, and amphoteric surfactants derive thek water solubiUty from thek ionic charge, whereas the nonionic hydrophile derives its water solubihty from highly polar terminal hydroxyl groups. Cationic surfactants perform well in polar substrates like styrenics and polyurethane. Examples of cationic surfactants ate quaternary ammonium chlorides, quaternary ammonium methosulfates, and quaternary ammonium nitrates (see QuARTERNARY AMMONIUM compounds). Anionic surfactants work well in PVC and styrenics. Examples of anionic surfactants ate fatty phosphate esters and alkyl sulfonates. 

Sliver. Frepd by addn of Ag nitrate soin to a soln of the Na salt (see above) (Refs 3 10) ign point 181° (Ref 12). When treated with alkyl iodides it gives alkyl esters. From the reaction with Me iodide a colorless and a yellow dimethyl ester were isolated (Ref 3). The UV spectra of the colorless (called a) and the yellow (called 3) esters are given in Ref 9 it is concluded that the color of the / ester is due to a nitroso group, hence its structure is probably (CH301 Q2CH2... 

In some cases it is possible to differentiate between the various alkyl substituents. Primary, secondary and tertiary nitrates and nitrites all show clearly different infrared absorptions. The spectra of acid fluorides can be used to differentiate chain-end groups from pendant acid groups. Furthermore, the loss of all -OH species upon sulfur tetrafluoride exposure allows the reliable estimation of ketones, esters and lactones without the complication of hydrogen-bonding induced shifts in the spectra. Preliminary results from the use of these reactions to characterize y-ray oxidized polyethylene and polypropylene are used to illustrate the scope of the methods. 

These compounds contain the fragment R as an alkyl or aryl moiety. In other words, they result from the esterification of an alcohol or a phenol with nitrous acid, nitric acid, phosphoric acid, sulfuric acid, or sulfamic acid, respectively. Many of the esters to be examined in this chapter must be activated prior to eliciting their effects, e.g., the organic nitrites and nitrates, which act as donors of nitric oxide or an analogous molecule, and phosphates, which are activated by hydrolysis or even by phosphorylation (antiviral agents). Sulfates are very seldom active or used as prodrugs, but they have significance as metabolites and as industrial xenobiotics. 

Feuer and co-workers ° conducted extensive studies into alkaline nitration with nitrate esters, exploring the effect of base, time, stoichiometry, concentration, solvent, and temperature on yields and purity. Reactions are generally successful when the substrate a-proton acidity is in the 18-25 p A a range. Alkoxide bases derived from simple primary and secondary aliphatic alcohols are generally not considered compatible in reactions using alkyl nitrates. Optimum conditions for many of these reactions use potassium tert-butoxide and amyl nitrate in THF at —30 °C, although in many cases potassium amide in liquid ammonia at —33 °C works equally well. 

Synthesis of nitrate esters from the reaction of alkyl halides with silver nitrate... 

McKillop and Ford synthesized a range of primary and secondary alkyl nitrates in excellent yields by treating alkyl bromides with mercury (I) nitrate in 1,2-dimethoxyethane at reflux (Equation 3.9). This method has been used to synthesize substituted nitrate esters from both a-bromocarboxylic acid and a-bromoketone substrates. Unlike metathesis with silver salts, which are widely known to promote SnI reactions, this method is not useful for the synthesis of nitrate esters from tertiary alkyl halides. 

Marans and co-workers used pentaerythritol trinitrate (81) to synthesize a number of aryl and alkyl esters, including the formate, propionate (84), oxalate, succinate, benzoate (85), 3,5-dinitrobenzoate (86), and ortho-, meta-, and para- (87) nitrobenzoate esters. The para-nitrobenzoate ester (87) has also been prepared from the nitration of pentaerythritol monobenzoate with mixed acid. ... 

Alkyl lV,lV-dinitramines (154) have been prepared from the reaction of the tetraalkylam-monium salts (155) of primary nitramines with nitryl fluoride in acetonitrile at subambient temperature. The same reaction with the primary nitramine or its alkali metal salts yields the corresponding nitrate ester. Treatment of the ammonium, potassium, or lithium salts of primary nitramines (156) with a solution of nitronium tetrafluoroborate in acetonitrile at subambient temperature yield alkyl iV,iV-dinitramines. ° The same reactions in ether or ester solvents enables the free nitramine to be used. The nitrolysis of A-alkylnitramides (157) and N,N-diacylamines with nitronium tetrafluoroborate in acetonitrile, and the nitration of aliphatic isocyanates with nitronium tetrafluoroborate and nitric acid in acetonitrile, also yield alkyl A,A-dinitramines (154). 

Alkyl azides are conveniently prepared from the reaction of alkali metal azides with an alkyl halide, tosylate, mesylate, nitrate ester or any other alkyl derivative containing a good leaving group. Reactions usually work well for primary and secondary alkyl substrates and are best conducted in polar aprotic solvents like DMF and DMSO. The synthesis and chemistry of azido compounds is the subject of a functional group series. ... 

Mannitol hexanitrate is obtained by nitration of mannitol with mixed nitric and sulfuric acids. Similarly, nitration of sorbitol using mixed acid produces the hexanitrate when the reaction is conducted at 0—3°C and at —10 to —75°C, the main product is sorbitol pentanitrate (117). Xylitol, ribitol, and L-arabinitol are converted to the pentanitrates by fuming nitric acid and acetic anhydride (118). Phosphate esters of sugar alcohols are obtained by the action of phosphorus oxychloride (119) and by alcoholysis of organic phosphates (120). The 1,6-dibenzene sulfonate of D-mannitol is obtained by the action of benzene sulfonyl chloride in pyridine at 0°C (121). To obtain 1,6-dimethanesulfonyl-D-mannitol free from anhydrides and other by-products, after similar sulfonation with methane sulfonyl chloride and pyridine the remaining hydroxyl groups are acetylated with acetic anhydride and the insoluble acetyl derivative is separated, followed by deacetylation with hydrogen chloride in methanol (122). Alkyl sulfate esters of polyhydric alcohols result from the action of sulfur trioxide—trialkyl phosphates as in the reaction of sorbitol at 34—40°C with sulfur trioxide—triethyl phosphate to form sorbitol hexa(ethylsulfate) (123). 

Investigating the types of reaction between nitric acid esters and hydrazine Merrow and van Dolah endeavoured first of all to solve the problem of how nitric acid is formed since the answer could in effect make it possible to establish the position of the linkage to be broken off in an ester molecule. They have established experimentally that during the reaction between alkyl nitrates and hydrazine the nitrite ion is produced very quickly. Later it dwindles away as reaction proceeds. The creation of NO in this process can never arise from the removal of a hydrogen atom in the a-posi-tion, since only an insignificant amount of ester can follow the reaction (31) to form an aldehyde ... 

It can be concluded from these experimental results that in alkaline media the 2-octyl nitrate behaves like a typical ester (Day and Ingold (50]). In neutral media, on the other hand, it behaves like an alkyl halogenide or like an ester of sulphuric acid. 

This is rather surprising because primary nitroalkanes (which would give more stable alkyl radicals) are not readily reduced by tin hydride. The third example in Scheme 43 illustrates a cyclization of an alkoxyl radical derived from a nitrate ester. 

Reaction intermediates formed in the nitration of a series of a,/i-unsaturatcd esters, such as (47), with N02BF4 have been reported to exhibit the expected behaviour of a-carbonyl cations. Three diagnostic reaction types were observed (1) Ritter reaction (2) cyclopropane formation from propyl cations (3) Wagner-Meerwein migration of alkyl groups. Semi-empirical calculations of the relative gas-phase stabilities of the proposed intermediate cations have also been performed.53... 

Methyla-arylacetates. These esters have been obtained by oxidative rearrangement of alkyl aryl ketones with thallium(III) nitrate in acidic methanol or trimethyl orthoformate (4,496 5, 656 7, 362). A new method, which avoids the toxic TTN, is based on the Woodward version of the Prevost reaction. Thus, treatment of the ketone with iodine (or bromine) and silver nitrate (2 equiv.) in refluxing methanol containing trimethyl orthoformate results in methyl a-arylacetates in 90% yield from simple substrates. Yields are lowered by electron-withdrawing substituents on the aromatic group and by a-branching in the alkyl group.2... 

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