DrDevice
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Phloramine synthesis from phloroglucinol
Hello all,
Long time lurker, first time post...
I have been experimenting for a while with hydroxy and methoxy substituted anilines, to subsequently form diazos, diazosulfonates, and phenylhydrazine
sulfonic acids, with modest success. Getting my first bright yellow precipitate was an extremely satisfying outcome, I have to say. I'll post some
procedures when I get around to it.
Anyway, one of the anilines I am trying to get is 3,5-dihydroxyaniline (otherwise known as phloramine):
I have found several references to synthesizing this from phloroglucinol
Some using ammonia gas, and various water or ethanol solutions thereof. I am getting better at translating German  - many of the diazo expts I have been doing are based on dyestuff manufacture from
the turn of the (last) century.
I have attempted several of these procedures, but just end up with a black tarry substance. 
There are notes regarding keeping air and moisture out, which I am doing with nitrogen gas.
Is there a way I can avoid the use of ammonia gas, or rather, generate it in-situ, and avoid water altogether? I am thinking about :
1. dissolve the phloroglucinol in (anhydrous) ethanol (phloroglucinol is readily soluble in ethanol)
2. Add NaOH and NH4Cl
3. Add MgSO4 to remove water of reaction from ammonia synthesis and NH2 substitution
4. The NH3 formed reacts in solution with the phloroglucinol
Do all this in a nitrogen atmosphere.
The NaOH and NH4Cl are only sparingly soluble in ethanol, so I expect this will take a while, but is this approach sensible? Will the
NH3 be "available" to react with the hydroxy group?
I am expecting the phloramine will stay in ethanol solution, and all the inorganic salts can be simply filtered out. Filtering this in an inert
atmosphere I haven't really thought about either...
Comments welcome...
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karlos³
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You could start from resorcinol and nitrate this with HNO3, then reduce the 5-nitro-3,5-dihydroxybenzene.
That would lead to phloramine.
You can even use some very mild reducing agents, as aromatic nitro groups are more easily reduced than aliphatic ones.
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shivam
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I doubt the nitration of resorcinol would yield a significant amount of 5-nitro-3,5-dihydroxybenzene
Theoratically, direct nitration of resorcinol should predominately yield Styphnic acid (2,4,6-trinitrobenzene-1,3-diol)
which could be justified by the fact that the negative charge density is the highest on the carbon that is adjacent to the hydroxyl group.
So I'm not sure that the nitration of resorcinol is the way to go..
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Boffis
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@ DrDevice; nitro-genes recently posted in the nitrobenzofuroxazan thread a synthesis of 3,5-dihydroxychlorobenzene from benzoquinone by a series of
"doable" steps. Would the halogen be reactive enough to replace with an amine group or something else that would act as an intermeadiate?
Nitration of resorcinol follows the o-p protocol so if you managed to stop the nitration at the mono stage you would get mainly 4 and lesser 2 nitro
nitroresorcinol, then 2,4 and 4,6 dinitro and finally 2,4,6 trinitroresorcinol but very little 5 substituted material. Do you have a reference for the
direct amination of phloroglucinol with ammonia? When this is done on naphthol derivatives it is usually done with aqueous ammonia and a small amount
of ammonium sulphite (ie ammonia solution with a little slphur dioxide dissolved in it) but it requires a pressurized reaction vessel.
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DrDevice
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G'day Boffis,
References for the direct amination include the following:
http://www.sciencemadness.org/talk/viewthread.php?tid=14031&goto=search&pid=229361
US Patent 2572284
https://archive.org/stream/treatiseonchemis33roscrich/treati...
There are references (I don't have them at hand) describing this reaction as a Bucherer reaction, which is very much the napthol based route.
Reference
"Name Reactions in Organic Chemistry" by Surrey describes that this route is not applicable to phenols "...with the exception of ...
phloroglucinol. I tried this method. Still black
I didn't say it before, but I have the phloroglucinol on hand (its used as a plant cell growth factor) - so the resorcinol route is interesting, but
not my prime aim. I will have a look at the benzoquinone route however.
My basic question regarding the generation of ammonia in-situ in non-aqeous solution remains.
Follow up - I have tried this, but without the MgSO4. I also attempted to get to get to the hydrochloride salt (allegedly more stable in air/water)
without isolating and dehydrating everything, and made a mistake with my calcs and put in way too much hydrochloric acid
I'm going to repeat with the MgSO4 include - I'll followup when I have some results.
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Boffis
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Hi DrDevice, The first link to an SM page doesn't seem to work, could you just give me the thread title and page.
I downloaded the patent and its certainly interesting it uses aqueous ammonia and ammonia gas, there is no need for the gas to be dry or to work at
elevated temperatures or pressures. The key is clearly exclusion of air, to which the free base is obviously sensitive, until you are in a position to
acidify with HCl. Since you can't "boil out" ammonia solution like you can a salt solution to get rid of the oxygen dissolve in it I wonder if you
could add an oxygen scavenger such as freshly precipitated ferrous hydroxide or precipitated iron (from ferrous chloride and sodium borohydride) to
the initial ammonia solution. I can see this being a workable process but you will need to design your experiment carefully first to ensure oxygen
free ammonia. Remember time spent designing your experiment and save hours of wasted time and chemicals later!
E.g. since your ammonia gas does not need to be dry just oxygen free ammonia try the reaction of slaked lime with ammonium chloride. Degass the fine
powdered slaked lime but placing it in the reaction flask and sucking out the air, allow in your inert gas and clamp the gas inlet and outlet shake
gently and when the dust settles, repeat this process a couple of times. The last bit of oxgen can be removed by adding a trace of ferrous chloride or
sulphate to the boiled ammonium chloride solution before adding to the slaked lime. Alternatively just slurry the lime with water and boil in a flask
and then cool attached to the inert gas supply before adding the boiled ammonium chloride solution.
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DrDevice
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The SM thread is titled "Quinone to make Energetic Compound" posted by the destructive thugs over in Energetic Materials 
OK, I can well believe that the oxygen is an issue. The patent talks about saturating with NH3, which I expect is driving any dissolved oxygen out of
solution.
Using NH4Cl & NaOH, I can't seem to get ammonia generation happening vigorously enough to get actual "bubbles" of ammonia appearing in the final
solution. It only starts once I heat it quite heavily. I'll see how I go with Ca(OH)2.
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DrMethyl
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Quote: Originally posted by karlos³  | You could start from resorcinol and nitrate this with HNO3, then reduce the 5-nitro-3,5-dihydroxybenzene.
That would lead to phloramine.
You can even use some very mild reducing agents, as aromatic nitro groups are more easily reduced than aliphatic ones. |
You cannot do that, because nitro will go to the ortho/para position.
I don't think the reaction is possible as describe (IMO) because the condition to convert phenols to anilines must be very drastic like very high
ammonia pressure.
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