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Author: Subject: DDNP & related compounds: The über thread!
nitro-genes
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[*] posted on 7-1-2018 at 13:17


Hypochlorite mediated oxidation of 2,3,6 trinitro-4-aminophenol to a furoxan might be tricky due to the ease of hydrolysis of any possible quinone-imine formed under these conditions due to OH/NH2 group in para, likely formation of chloropicrin from nitrophenols in general and the well described incompatibility of the compound with bases, decomposing to form tarry products.

Going through the excerpts posted, it seems any possible furazan/furoxan from the nitration of isopicramic acid could be harder to distinguish from a diazophenol than I thought, potentially sharing similar melting points, colour, explosion temp, solubility in strong acids and light sensitivity. :D

I wondered if the trinitrodiazophenol obtained from the nitration of isopicramic acid may rearrange in water or under slightly basic conditions to a benzofurazan/furoxan as opposed to only displacement of the 3-nitro by water or OH-, but can't figure out a likely mechanism, since it would entail a series of complex rearrangements not generally known for diazo(nium) groups and unlikely maybe due to the para orientation of the OH/NH2 group. Couldn't find any examples of furazan/furoxan formation from diazonium precursors in literature at least, except via azide substitution of the diazo group and oxido-redox with an ortho nitrogroup, like in the synthesis of KDNP, which probably doesn't occur through a quinone-imine precursor in the first place. The latter also suggests that any furoxan formed wouldn't react further with the excess azide used in some reaction schemes outlined, which directly contradicts the observed formation of nitrogen for the compound obtained from further nitration of isopicramic and seems the best argument the compound truly is a diazophenol. Moreover, the in literature described "boiling dilute SA-excess nitrite treatment" of mono and dinitro-4-amino resorcinol derivatives also results in a compound that forms salts, which would be hard to explain as a furazan/furoxan without an extra nitro group present ortho relative to the amino group after nitration, which seems very unlikely to occur under these conditions.

As an interesting side note, I subjected 2-nitro 4-diazophenol to the "boiling 30% SA-excess nitrite" treatment and obtained a product which proved very similar to pDDNP with regard to oxygen balance, so definitely a second nitro group was introduced. Where was it likely to end up? Position 3,5 or 6? :P


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Rosco Bodine
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[*] posted on 9-1-2018 at 01:16


The acetaminophen derivative I thought likely to form a possible phenolic analogue of KDNBF would be the 3-nitro derivative of paracetamol acetate where the ortho related 3-nitro and 4-amino (after deacetylation) would provide the structure susceptible to oxidation by hypochlorite as occurs for the o-nitroaniline precursor oxidized to benzofuroxan and further nitrated for KDNBF.

If there is possible a HO-DNBF it would be somewhat analogous to the HO-DDNP or DDNR, only it should be a diacid. When a hydroxyl is added to the ring for DDNP or p-DDNP it results in a better oxygen balance and increased energy, so it seems that could be true also when a hydroxyl is added to the ring of DNBF.

Use of acetic anhydride to form paracetamol acetate directs the first nitro group to 3 and forms the needed ortho relation of nitro and amino as would occur for the o-nitroaniline precursor for KDNBF.

[Edited on 1/9/2018 by Rosco Bodine]
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Rosco Bodine
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[*] posted on 11-1-2018 at 23:17


@nitro-genes

Reviewing some of the earlier research hasn't been done so I am going on memory but there was a Japanese Pharmaceutical Bulletin article that misidentified a 3-nitro derivative of paracetamol, that was instead actually a 3-nitroso. If they got the structure correct for the ring position 3, then it seems possible a nitroso at 3 could be attached first and then the 3-nitroso could be converted to a 3-nitro. It may be that this was discussed at the earlier time and ruled out for some reason. I recall there were issues with duplication of that reported synthesis, but have wondered if a conventional nitrosation approach would not also introduce a nitroso at 3 on paracetamol. If it does work then that could be used to avoid the requirement for acetic anhydride to form paracetamol acetate and get selective reaction on position 3 for the entering group.

Position 3 nitration is the key pathway for DDNR and iso-DDNR and for the speculative hydroxy KDNBF if it exists.
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