Synthesis, Characterization And Preliminary Performance Of Energetic Pyridine Derivatives

In this paper, the synthetic routes, characterization and theoretical studies of energetic pyridine-based materials were studied systematically, especially [1,2,5]oxadiazolo[3,4-e]-tetrazolo[1,5-α]pyridine-3-oxide,2-amino-3,5-dinitro-6-substituted pyridine derivatives, 2-substituted-4-amino-3,5-dinitropyridine derivatives,2,6-disubstituted-4-amino-3,5-dinitro-pyridine derivatives and cyclourea nitroamine derivatives containing the pyridine or benzene ring.An intermediate [1,2,5]oxadiazolo[3,4-e]tetrazolo[1,5-α]pyridine-3-oxide(88b) was described using 2,6-dichloropyridine as a primary material. The structural stability of this compound was discussed, which revealed that the furoxano group was stable under the conditions of strong acid, strong base and weak base, but the tetrazolo group formed by azido group at ortho-position of the pyridine ring was unstable, and easily attached by electron-donating groups such as hydroxy, methoxy, methylamino.A novel synthetic route of 2-amino-3,5-dinitro-6-chloropyridine and its derivatives was designed and described starting from cheap and easily available 2,6-dichloropyridine, followed by nitration, amination and again nitration reaction, and then attached by several nucleophilic reagents, such as ammonia, sodium azide to form energetic 2-amino-3,5-dinitro-6-substituted pyridine derivatives:2,6-diamino-3,5-dinitropyridine(20),2,6-diamino-3,5-dinitropyridine-1-oxide(21),5-amino-6,8-dinitrotetrazolo[4,5-a]pyridine (102b),5-amino-6-nitro-[1,2,5]oxadiazolo[3,4-6]pyridine-l-oxide(103), N2-(6,8-dinitro-tetrazolo[1,5-a]pyridin-5-yl)-2,6-diamino-3,5-dinitropyridine(106). The results show that the synthetic route has the advantages of easy-obtained raw materials, simple work-up and high purity product.Facile synthetic routes for the preparation of 2-chloro-4-amino-3,5-dinitropyridine and its derivatives had been designed and revealed. Nitration of 2-chloro-4-aminopyridine as a starting material, in an unexpected one-step reaction, to a dinitrated derivative 2-chloro-4-amino-3,5-dinitropyridine(111) and (E)-1,2-bis(2-chloro-3-nitropyridin-4-yl)di azene(112).2-chloro-4-amino-3,5-dinitropyridine could react with nucleophilic reagents, such as sodium azide, potassium fluoride, ammonia, methylamine,4-nitroimidazol to give a series of energetic 2-substituted-4-amino-3,5-dinitropyridine derivatives:(E)-1,2-bis(2-amino-3-nitropyridin-4-yl)diazene(113),2,4-diamino-3,5-dinitropyridine(114),7-amino-6-nitro-[1,2,5] oxadiazolo[3,4-b]pyridine-l-oxide(115),7-amino-6,8-dinitrotetrazolo[1,5-α]pyridine(116b). It was of significance that all of the nucleophilic substitution reactions were carried out under mild conditions and easy work-up.A novel synthetic route of 2,4,6-triamino-3,5-dinitropyridine-l-oxide was described using 2,6-dichloropyridine as a starting material, followed by oxidation, nitration, reduction and again nitration reaction to give 2,6-dichloro-3,5dinitro-4-aminopyridine(129) as an intermediate, and the target compound was then obtained by amination and oxidation reaction.The synthesis of energetic cyclourea compounds based on the pyridine ring and the benzene ring had been describled. 1,3,5-trinitro-1,3-dihydro-2H-imidazo-[4,5-b]pyridin-2-one(155) was synthesized using 2,3-diaminopyridine as a primary material, followed by ring-closing reaction and nitration reaction. Besides, two synthetic routes for the preparation of 5-amino-1,3,6-trinitro-1H-benzo[d]imidazol-2(3H)-one(160) as the energetic material had been revealed. Direct nitration of 5-amino-1H-benzo[d]imidazol-2(3H)-one gave the trinitrated 5-amino-1,3,6-trinitro-1H-benzo[d]imidazol-2(3H)-one in a poor yield of 11%; and indirect synthetic reaction of N-protected reaction, nitration, deprotection and again nitration reaction with an overall-yield of 48%.