Nitration of 5-methyltetrazole
various starting materials such as 2-methylimidazole,
2-methoxy-2-methyl-imidazolidine-4,5-dione,and2-methylpyrimidine-4,6-dione(4,5-dihydroxy-2-methylpyrimidine) were nitrated and then hydrolyzed to give
FOX-7 by somewhat different process. Since the methyl group was converted to dinitromethylidene moiety in all methods, nitration of 5-methyltetrazole
was attempted to afford 5-dinitromethylidene-1,4-dihydrotetrazole. But this reaction failed to proceed, and most of the starting material was
recovered.
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With the necessary intermediates in hand, we sought to construct the N2FOX-7 using decarboxylation and elimination. Thus, various conditions were
tried. When ethyl 5-tetrazolyldinitro-acetate was treated with water, 5-dinitromethyltetrazole was readily given. Hydrolysis followed by
decarboxylation took place completely within 2 h at 50 °C.
Synthesis and Characterization of High EnergeticTetrazole and Furoxan Derivatives, (Korea)
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ethyltetrazolylacetate
N4HC-CH2-C(=O)-O-CH2CH3
The reason that the nitration of 5-methyltetrazole failed to proceed is probably the same reason that nitration of plain 1,2,3-triazole is essentially
impossible.* I suspect that the electron-withdrawing tetrazole ring pulls away electric charge from the methyl group, giving it a partial positive
charge and effectively shielding it from interaction with nitronium ions, which is the mechanism of reaction in most nitrations.
*In contrast, 4-nitro-1,2,3-triazole is easily both nitrated, and oxidized interestingly, by normal mixed HNO3/H2SO4 acids to
4,5-dinitro-1,2,3-triazole-N-oxide. The addition of one nitro group appears to activate the other CH to nitration.
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