Quinoline 1-oxides nitration

These compounds are convenient starting materials for the preparation of a wide variety of platinum(II) complexes. The chlorine atoms can be replaced by other negative groups such as bromide, iodide, hydroxide, nitrate, nitrite, and thiocyanate. The ammonia molecules can be replaced by other bases such as pyridine, arylamines, and quinoline. Oxidation with aqua regia or chlorine yields the corresponding isomers of tetrachlorodiammineplatinum(IV) (synthesis 62). A supposedly third (7-) form has been shown to be a solid solution or mixture of the cis (jS-) and trans (a-) isomers. 

Previous reports have indicated that 2-phenylquinoline A-oxide nitrates at the 4-position. However, it is now clear, although for reasons not yet understood, that the site of nitration varies with the reaction conditions. For example, 2-(3-nitrophenyl)quinoline iV-oxide is always produced, albeit in variable yield (27— 78%), in 80— 95% sulphuric acid regardless of the reaction temperature. In contrast, 4-nitro-2-phenylquinoline JV-oxide is the main product (19—35%) in more dilute (70—75%) sulphuric acid. N-Amino-quinolinium, -isoquinolinium, and -phenanthridinium salts, with base, give not the anticipated N-imides but their dimers, e.g. (106). ° Despite the fact that the 7V-imide monomers cannot be... 

This method is exemplified by its application to quinoline, isoquinoline, cinnoline, and isoquinoline 2-oxide, which are nitrated as their conjugate acids. The rate profiles for these compounds and their N- or O-methyl perchlorates show closely parallel dependences upon acidity (fig. 2.4). Quaternisation had in each case only a small effect upon the rate, making the criterion a very reliable one. It has the additional advantage of being applicable at any temperature for which kinetic measurements can be made (table 8.1, sections B and D). 

These arguments were originally applied to the 4-nitration of 2,6-lutidine i-oxide and quinoline i-oxide, and use of the data available... 

Because of these difficulties, special mechanisms were proposed for the 4-nitrations of 2,6-lutidine i-oxide and quinoline i-oxide, and for the nitration of the weakly basic anilines.However, recent remeasurements of the temperature coefficient of Hq, and use of the new values in the above calculations reconciles experimental and calculated activation parameters and so removes difficulties in the way of accepting the mechanisms of nitration as involving the very small equilibrium concentrations of the free bases. Despite this resolution of the difficulty some problems about these reactions do remain, especially when the very short life times of the molecules of unprotonated amines in nitration solutions are considered... 

Ochiai and Okamoto showed that nitration of quinoline i-oxide in sulphuric acid at o °C gave 5- and 8-nitroquinoline i-oxides with a trace of the 4-isomer, but that at 60-100 °C 4-nitration became overwhelmingly dominant. The orientation depends not only upon temperature but also upon acidity, and kinetic studies (table 8.4 table 10.3) show that two processes are occurring the nitration of the free base (vil, R = O at C(4), favoured by low acidities and high temperatures, and the nitration of the cation (vil, R = OH), favoured by high acidities and low temperatures. ... 

Doebner-von Miller synthesis, 2, 466 hydrazination, 2, 238 NMR, 2, 120 Quinoline, 5-methyl-nitration, 2, 50, 318 Quinoline, 6-methyl-mercuration, 2, 321 N-oxide... 

Quinoline, 5-nitro-oxidation, 2, 210 synthesis, 2, 318 Quinoline, 6-nitro-nitration, 2, 318 Quinoline, 7-nitro-nitration, 2, 318 synthesis, 2, 318 Quinoline, 8-nitro-... 

Ewins has synthesised both substances from m-methoxybenzoic acid, which on nitration gave 2-nitro-3-methoxybenzoic acid, and this, on reduction and treatment with methyl iodide, yielded damasceninic acid, which, by esterification with methyl alcohol, furnished damascenine. Kaufmann and Rothlen found that the additive product of 8-methoxy-quinoline and methyl sulphate, on oxidation with permanganate, yields formyldamasceninic acid, MeO. CgH3(NMe. CHO). COOH, which can be transformed into damasceninic acid by warming with dilute hydrochloric acid. ... 

The nitration of l,2,5-selenadiazolo[3,4-/] quinoline 77 with benzoyl nitrate affords the 8-nitro derivative 78, whereas methylation with methyl iodide or methyl sulfate afforded the corresponding 6-pyridinium methiodide 79 or methosulfate 80, respectively (Scheme 29). The pyridinium salt 80 was submitted to oxidation with potassium hexacyanoferrate and provided 7-oxo-6,7-dihydro derivative 81 or, by reaction of pyridinium salt 79 with phenylmagnesium bromide, the 7-phenyl-6,7-dihydro derivative 82. Nucleophilic substitution of the methiodide 79 with potassium cyanide resulted in the formation of 9-cyano-6,9-dihydroderivative 83, which can be oxidized by iodine to 9-cyano-l,2,5-selenadiazolo [3,4-/]quinoline methiodide 84. All the reactions proceeded in moderate yields (81IJC648). 

Oxidation of 5-arylazo-6-aminoquinoline 146 with copper sulfate in pyridine gave the corresponding 2-aryltriazolo[4,5-/]quinolines 147. Condensation of halo-genated nitrobenzenes with triazolo[4,5-/]quinoline 145 yielded the appropriate 2H- and 3//-aryl derivatives. The nitration of 3-phenyl-3//-triazolo[4,5-/]quino-line 147 occurred at position 4 of the phenyl ring (Scheme 46) (73T221). 

The use of cerium(IV) ammonium nitrate (CAN) as a catalyst for an aza-Diels-Alder reaction was reported in two different publications. In one report Perumal and co-workers react a variety of anilines 86 and aldehydes 87 with enamine 88 in the presence of 5 mol% CAN to form a series of tetrahydroquinolines 89. The reactions were performed at room temperature with very short reaction times and in good yields. In addition, the resulting tetrahydroquinolines could be oxidized to the corresponding substituted quinolines using 2.5 eq of CAN in high yields <06TL3589>. 

Nitration of pyridines in other than nitric or sulfuric acids is of little interest here because either no reaction or N-nitration takes place (see Section 2.05.2.10). However, pyridine 1-oxide is considerably more reactive and treatment with benzoyl nitrate ultimately leads to the 3-nitro derivative (Scheme 25) (60CPB28). Annelation of a benzene ring bestows greater reactivity on the 3-position in quinoline, compared with pyridine, and reaction with nitric acid in acetic anhydride furnishes the 3-nitro derivative (ca. 6%) (Scheme 26). This isomer has also been obtained, again at low yield (6-10%), by treatment of quinoline with tetranitratotitanium(IV) in carbon tetrachloride (74JCS(P1)1751>. Nitration of benzo analogues of pyridine occurs much more readily in the benzene ring, and Chapter 2.06 should be consulted for these reactions. 

Benzo[/]quinoline (13 R=H) on nitration at -15 °C gives 7-nitrobenzo[/]quinoline (40%) (13 R = N02) together with smaller amounts of the 10- (13%) and 9-nitro derivatives (9%). At 0 °C the 7,9-dinitro derivative is obtained. Nitration of benzo[/]quinoline AT-oxide gives 7-nitrobenzo[/]quinoline Af-oxide. 

In other compounds, reaction can occur in both rings. Under such circumstances the orientation can depend on the conditions frequently reaction in the benzene ring involves the cationic species, whereas that in the pyridine ring involves the free base. Thus, the temperature dependent nitration of quinoline 1-oxide (578) reflects the decrease in intrinsic acidity as the temperature rises, which in turn increases the available amount of free base species. 

In recent years, the reactivities of thieno[2,3-c]pyridine and its fused analogs have received considerable attention. Nitration of thieno[2,3-c]quinoline 5-N-oxide (225) gives rise to 1-nitro derivative 226 (1989CS305), whereas bromination affords a mixture of bromide 227 and dibromide 228 (1989CS309). 

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