Nitration with nitronium chloride

Urbanski and Siemaszko [75] examined the nitration of cellulose with NO2CI in the vapour phase. Gaseous NO2CI was drawn through cellulose at 20°C for 4 hr, and the nitrocellulose than subjected to the usual treatment. A product with 12.2% N was obtained with 168% yield. The product does not contain chlorine. Its stability is higher than that of nitrocellulose of the same nitrogen content prepared by means of the usual nitrating mixture. 

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Nitration of cellulose in the gaseous phase Nitration with nitronium chloride Kinetics of nitration. Heat of reaction Heat of nitration... 

Chlorosulfonation of benzotrichloride with chlorosulfonic acid (28) or with sulfur trioxide (29) gives y -chlorosulfonyl benzoyl chloride [4052-92-0] in high yield. Nitration with nitronium fluoroborate in sulfolane gives 68% y -nitro-benzotrichloride [709-58-0] along with 13% of the ortho and 19% of the para isomers (30). 

In Lewis acid halide catalyzed nitrations with nitryl chloride the question arises are these reactions nitronium salt nitratiors according to the ionization... 

Olah and coworkers56 found that treatment of dialkyl, arylalkyl and diaryl sulphides with nitronium hexafluorophosphate (or tetrafluoroborate) 32 at —78° in methylene chloride resulted in the formation of sulphoxides in moderate to high yields (Table 3). In the oxidation of diphenyl sulphide which affords diphenyl sulphoxide in 95% yield, small amounts of the ring nitration products (o- and p-nitrophenyl phenyl sulphides) were formed. However, diphenyl sulphone and nitrophenyl phenyl sulphoxide were not detected among the reaction products. 

Trinitrochlorobenzene (picryl chloride) (87) can be prepared from the nitration of 2,4-dinitrochlorobenzene with nitronium tetrafluoroborate or mixed acid composed of fuming nitric acid and oleum. Picryl chloride is also synthesized from the reaction of phosphorous oxychloride with the pyridinium salt of picric acid. ... 

While nitramines are formed from the reaction of secondary amines with nitronium salts the success of the reaction depends on the basicity of the amine (Equation 5.11). Thus, amines of low to moderate basicity are A-nitrated in good yields. The nitration of more basic amines is slow and the nitrosamine is often observed as a significant by-product, a consequence of the partial reduction of the nitronium salt to the nitrosonium salt during the reaction. Increased reaction temperature is also found to increase the amount of nitrosamine formed. The amine substrate is usually used in excess to compensate for the release of the strong mineral acid formed during the reactions. Both nitronium tetrafluoroborate and the more soluble hexafluorophosphate are commonly used for A-nitrations. Solvents like acetonitrile, methylene chloride, nitromethane, dioxane, sulfolane, ethyl acetate and esters of phosphoric acid are commonly used. 

Ammonium dinitramide (152) is synthesized by treating a solution of ammonium ni-trourethane (150) with nitronium tetrafluoroborate or dinitrogen pentoxide in methylene chloride at -30 °C, followed by ammonolysis of the resulting ethyl A,lV-dinitrourethane (151)7 Ammonium dinitramide can be prepared from the nitration of ethyl carbamate and ammonium carbamate with the same reagents. This is currently the most efficient route to ammonium dinitramide and is used for its manufacture (Section 9.11). 

Electrophilic nitration of olefins can also be carried out with nitronium salts in pyridinium poly (hydrogen fluoride) (PPHF) solution491 (which also acts as solvent) to give high yields of nitrofluorinated alkanes. In the presence of added halide ions (iodide, bromide, chloride) the related haloalkanes are formed, and these can be dehydrohalogenated to nitroalkenes492 [Eq. (5.183)]. 

Reaction of a primary aliphatic amine, n-butylamine, with nitronium tetrafluoroborate in methylene chloride or acetonitrile produced not n-butylnitramine, but n-butyl nitrate in about 20% yield. However, treating an electronegatively substituted primary aromatic amine, picramide, with nitronium tetrafluoroborate did give the primary nitramine, N,2,4,6-tetra-nitroaniline, in 85% yield. Olah (16) had reported previously that aniline was oxidized vigorously by nitronium salts. 

In order to study this problem, Olah and Lin carried competitive studies of nitration of benzene and toluene with nitry chloride, catalyzed by Lewis acid halides. When carbon tetrachloride or excess aromatics were used as solvent, the data summarized in Table XII were obtained. The data show that the ortho para ratios are smaller than in nitrations with nitio-nium salts. The observed changes point to the fact that the nitrating agents arc the conesponding donor acceptor complexes and not the nitronium ion itself. The lower orthojpara ratios than those obtained in case of NOj, particularly point to bulkier nitrating agents. 

Nitroxanthine is produced is produced as the major nitration product in reactions of 2 -deoxy-guanosine or ca//thymus DNA with nitryl chloride produced by mixing nitrite with hypochlorous acid, and 8-nitroguanidine was a minor product in these reactions (Chen et al. 2001). Formation of 8-nitroxanthine was also detected by xanthine reaction with various reactive nitrogen species, including nitryl chloride, peroxynitrite, nitronium tetra-fluoroborate, and heated nitric and nitrous acids. 

Further work by Baum and co-workers showed that the nitration of l,l-diamino-2,2-dinitroethylenes with trifluoroacetic anhydride and nitric acid in methylene chloride yields 1,1,1-trinitromethyl derivatives via addition of nitronium ion to the double bond of the enamine such treatment also resulting in the A-nitration of the products. In this way, trini-tromethyl derivatives like (185) and (188) are obtained. Further treatment of these trinitromethyl derivatives with aqueous potassium iodide results in reductive denitration and the formation... 

The electrophilic substitution is the most characteristic reaction for these classes of compounds. Compound (21) undergoes standard electrophilic aromatic substitution reactions. Thus it forms the 6-bromo compound (58) with A7-bromosuccinimide and 6,7-dibromo compound (72) with the excess of the same reagent. It also forms the 6-nitro compound (67) with copper(II) nitrate trihydrate and 6,7-dinitro compound (68) with excess of nitronium tetrafluoroborate. The bis(trifluoro-acetoxy)thallium derivative (73) was formed from trithiadiazepine (21) and thallium(III) trifluoro-acetate in refluxing acetonitrile. Without isolation, (73) was directly converted into the pale yellow 6-iodo compound (74) with aqueous potassium iodide, into the 6-cyano compound (75) with copper(I) cyanide, and into methyl trithiadiazepine-6-carboxylate (76) with carbon monoxide and methanol in the presence of palladium chloride, lithium chloride, and magnesium oxide. Compound (21) is acetylated in the presence of trifluoromethanesulfonic acid (Scheme 7) <85CC396,87JCS(P1)217, 91JCS(P1)2945>. 

Witryl fluoride is a more powerful nitrating agent than nitryl chloride, but is more difficult to handle. Hetherington and Robinson [42] reported nitration of aromatics with nitryl fluoride in the absence of catalysts. They suggested that in solution, nitryl fluoride di dates into NO2 and and the intermediate nitronium ion thus formed is the active reagent in the nitrations. Less reactive aromatics such as nitrobenzene were not nitrated and considerable tar formation occurred during the reactions. We found... 

A solution of a stable nitronium salt (generally the hexafluorophosphate NOa PF but also the hexafluoroantimonateNO SbFft ortetrafiuoroborate NO2BF4) in methylene chloride-tctramethylene sulfone solution was allowed to react with the alkane (cycloalkane), with usual precautions taken to avoid moisture and other impurities. Reactions were carried out at room temperature (25°C) in order to avoid or minimize the possibility of radical side reactions and/or protolytic cleavage reactions (tertiary nitroalkanes particularly readily undergo protolytic cleavage, even if the system initially is acid free but nitration forms acid). Data obtained are summarized in Table XXI. 

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