3.5- Dinitropyridine, amination

As an extension of this work, the aminodechlorination of 2-chloro-3,5-dinitropyridine was studied (85JOC484). Because of the high 77-electron deficiency of this compound, it appears that the amination does not require the presence of a strong nucleophilic amide ion liquid ammonia is already... 

The direct nitration of 2,6-diaminopyridine (168) with mixed acid yields 2,6-diamino-3,5-dinitropyridine (ANPy) (173). Oxidation of ANPy (173) with peroxyacetic acid yields ANPyO (174) (calculated VOD 7840 m/s, d = 1.88 g/crc ) C-Amination of ANPyO (174) with hydroxylamine hydrochloride in aqueous base yields the triamine (175), an impact insensitive explosive of high thermal stability. ... 

Kinetic studies have been reported of the reactions of a series of 2-substituted-5-nitrothiophenes (substituent = Br, OMe, OPh, OC6H4-4-NO2) with secondary amines in room-temperature ionic liquids. The kinetic behaviour is similar to that of the corresponding reactions in methanol so that most reactions do not show base catalysis. The observation that reactivity is higher in the ionic liquids than in methanol (or benzene) is attributed to relatively poor solvation of the reagents by the ionic liquids. As in conventional solvents, 2-bromo-3-nitrothiophene shows higher reactivity than 2-bromo-5-nitrothiophene.42 Solvent effects on the kinetics of the alkaline hydrolysis of 2-phenylthio-3,5-dinitropyridine in aqueous organic solvents have been analysed.43... 

Due to its enhanced jr-deficiency 3,5-dinitropyridine has a lower site selectivity and it can be expected that oxidative amino-dehydrogenations will take place at all three positions 2, 4, and 6. This has indeed been found. 3,5-Dinitropyridine gives a complex mixture of 2-amino-, 2,6-diamino-, 2,4-diamino-, and 2,4,6-triamino-3,5-dinitropyridines (Scheme 5) (85JOC484, 93ACS95). Mixtures of diamino- and triamino-3,5-dinitropyridines have also been found in the oxidative amination of 2-R-3,5-dinitropyridines (R = NH2, OH, Cl, OMe) and 4-R-3,5-dinitropyridines (R = NH2, Cl). 

Amination of 2-chloro-3,5-dinitropyridine in liquid ammonia at —40°C and potassium permanganate gave 2,6-diamino-3,5-dinitropyridine. Its formation indicates that besides SNH at C-6, a SN(AE) amino-dechlorination occurs at C-2 (Scheme 6). 

NMR studies on a-adduct formation between 2-chloro-3,5-dinitropyridine and liquid ammonia show that the site of covalent addition is temperature dependent at — 60 °C the C-4 adduct is formed, at —40°C the C-6 adduct is obtained (85JOC484). Apparently, at — 60 °C the C-4 adduct is the kinetically favored one, and at —40°C the thermodynamically more stable C-6 adduct is obtained. The results are in agreement with those of the amination at —40 °C (Scheme 6). 

Oxidative aminatirMi of 2-anuno-3,5-dinitropyridine-l-oxide has recently been performed by using anmumia (gas), bubbling into a solution of this substrate and KMn04 in DMSO (Scheme 9) [54], 2-R-l,3,5-Triazapyrenes have been aminated with aqueous ammonia in dioxane in the presence of K3[Fe(CN)6] to give the corresponding 6-amino derivatives in 89-95% yield (Scheme 9) [55]. The reaction can also be carried out without dioxane as co-solvent, but in this case it requires a more time. 

In the second group of substances, the same investigation method was apphed to N,N -bis(2,4,6-trinitrophenyl)-3,5-dinitropyridine-2,6-diamine (PYX), 2,4,6-trinitroanihne (PAM), 2,4,6-trinitro-N-(2,4,6-trinitrophenyl)ani-line (DPA), and N,N, N"-tris(2,4,6-trinitrophenyl)-l,3,5-triazine-2,4,6-tri-amine (TPM) [183]. Figures 31a and 31b present the results obtained from the investigation of PYX, which also seem to confirm the suggested splitting process in Scheme 6. 

Since these early studies, numerous derivatives of 2-chloro- and 2-bromo ia, 672 and 4-chloro- and 4-bromo-pyridine 73 have been converted into amino- or alkylamino-pyridines under conditions differing little from those mentioned above. Modifications which have been used include the addition of copper sulphate as a catalyst a, 672a reaction in the presence of pyridine 64 and also, in the case of 4-chloropyridine, reaction with primary and secondary aliphatic amines in benzene 4 at 140-180 . The qualitative data from these numerous examples show the effect of other substituents upon 2- and 4-halogen atoms to be as expected. GarboxyM oa, 675, 9i8 and nitro-groups24ia markedly augment reactivity, and in a compound such as 2-chloro-3,5-dinitropyridine, much milder conditions than usual can be used for amination e ... 

Arylhydrazinopyridines do not undergo the benzidine rearrangement . They are easily oxidized to azo compounds, even by air. Preparatively the oxidation has been effected by alkali , mercuric oxide " , and by nitrous acid in acetic acid 2a, c, Surprisingly, 3,3, 5,5 -tetranitro-2,2 -hydrazopyridine is oxidized by silver acetate to 3,5-dinitropyridine 26 2-Arylhydrazinopyridine 1-oxides give 2-arylazopyridine 1-oxides in alkali, but boiled in alcohol or acetic acid they form 2-arylazopyridines . Recrystallization of 4,4 -hydrazopyridine l,T-dioxide picrate causes oxidation to the azo compound <. Arylhydrazinopyridines are reduced to the two primary amines by zinc and hydrochloric acid < ... 

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