Studies of novel nitro-substituted nitrogen heterocyclic compounds

Simon Philbin

Research output: Types of ThesisPhDpeer-review

Abstract

The novel candidate high energy insensitive explosive; 2,5-diamino-3,6-dinitropyrazine (ANPZ-i) (10) has been prepared in acceptable overall yield. ANPZ-i was synthesised by the nitration of 2,5-diethoxypyrazine (149, R=Et) using nitronium tetrafluoroborate (NO2+BF4-) in sulfolane and the subsequent amination of 2,5-diethoxy-3,6-dinitropyrazine (150, R=Et) under autoclave conditions. Oxidation studies towards the dioxide derivative of ANPZ-i, 2,5-diamino-3,6-dinitropyrazine-1,4-dioxide (PZDO) (11), were unsuccessful. The synthesis of existing high explosives; 2,6-diamino-3,5-dintropyrazine (ANPZ) (95) and 2,6-diamino-3,5-dinitropyrazine-1-oxide (PZO) (9) has been scaled up to produce approximately 25 g batches of material. A number of novel nitrations using NO2+BF4- have been carried out on a range of chloro-, methyl- and hydroxy-functionalised quinoxalines and quinazolines. A range of novel functionalisations have been carried out on the platform molecule 2,4-diamino-6,8-dinitroquinazoline (61) giving rise to 2,4-diamino-6,8-dinitroquinazoline-1,3-dioxide (141) (di-N-oxidation product), 2,4,7-triamino-6,8-dinitroquinazoline (142) (monoamination product) and 2,4,6,8-tetraaminoquinazoline (143) (dihydrogenation product). Detonics molecular modelling was carried out on the following target molecules: 2,5-diamino-3,6-dinitropyrazine-1,4-dioxide (PZDO) (11), 2,5,8-triamino-3,6,7-trinitroquinoxaline-1-oxide (151) and 2,5,7-triamino-4,6,8-trinitroquinazoline-1-oxide (138). The detonation velocity of the new explosive molecule; 2,5-diamino-3,6-dinitropyrazine (ANPZ-i) (10) was calculated and it was found to be a similar value to that obtained experimentally for the existing high explosive RDX (5). Calculation by molecular modelling of the steric energies of ANPZ (95), PZO (9), ANPZ-i (10) and PZDO (11) gave a quantitative assessment of the difficulty in oxidising ANPZ-i to give PZDO. Extensive analysis of carbon-13 NMR spectroscopy shift values was carried out for approximately twenty nitrogen heterocyclic compounds. Comparison of shift values indicated consistency in the interpretations. On-line literature searches have shown that the following compounds prepared in this project are new: 2,3,6-trichloro-5-nitroquinoxaline (120), 2,3-dimethoxy-6,7-dinitroquinoxaline (128), 2,3,6-trichloroquinoxaline-1-oxide (133), 2,4-diamino-6,8-dinitroquinazoline-1,3-dioxide (141), 2,4,7-triamino-6,8-dinitroquinazoline (142) and 2,5-diamino-3,6-dinitropyrazine (ANPZ-i) (10). Furthermore, new synthetic routes have been used in the preparation of the following compounds: 2,3-dichloro-5-nitroquinoxaline (118), 2,3,6,7-tetrachloro-5-nitroquinoxaline (123), 2-hydroxy-6-nitroquinoxaline (127), 2-hydroxy-3-methyl-6-nitroquinoxaline (126) and 2,5-diethoxy-3,6-dinitropyrazine (150, R=Et).
Original languageEnglish
Publication statusPublished - 1 Jan 2001
Externally publishedYes

Keywords

  • High energy insensitive explosive
  • 2,4-diamino-6,8-dinitroquinazoline-1,3-dioxide
  • Nitronium tetrafluoroborate
  • Quinazoline
  • Quinoxaline
  • Organic chemistry
  • Nitration
  • Nitrogen heterocyclic compound
  • Pyrazine
  • 2,5-diamino-3,6-dinitropyrazine

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