cactusmae
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reduce nitro aromatic compound to very polar amine
Product amine is very polar and has good solubility in water, so less amont of water is perferred for the reduction and workup steps. But for Zinc/HCl
or Fe/HCl procedure, it need water to dissolve the catalyst. How to solve this problem? Anybody know the best ratio of reaction or good work up steps
I can try. Product is sensative to strong base as well.
[Edited on 19-10-2011 by cactusmae]
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Picric-A
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Reduce with the usual Fe/HCl, freebase with NaOH, steam distill out the amine, extract with diethyl ether. Voila
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cactusmae
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But the product is strong base sensative. That is why I avoid of base reduction in the first place.
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Picric-A
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The reduction is an acidic reduction so should not harm your substrate.
The freebasing with NaOH, although a strong base, should not harm the substrate as it is being immedietly neutralised (if performed right)
Alternativly, use something like Ca(OH)2 as this should not harm your substrate at all.
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cactusmae
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Also the Fe/HCl reduction takes really long time. Should I heat up or add other cosolvent to speed up the reaction? My product has very big Mw, I
doubt the steam distillation will get it out. I tried the extraction, but with good solubility in water, low yield and poor purity product was got.
[Edited on 19-10-2011 by cactusmae]
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DJF90
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Have you tried Pd/C with hydrogen or under CTH conditions using ammonium formate? The reduction is performed in methanol or other organic solvent
(e.g. ethanol, ethyl acetate) and once complete (often evident from the colour change associated with reduction of the nitro group) the catalyst is
just filtered out and the product isolated by evaporation of the solvent. Provide more details about your substrate if you want a more helpful reply.
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cactusmae
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My substrate is perfluorinated carbon chain with brominate protected double bond. I tried to run the reduction and deprotection in one batch, which I
did successfully one time with Fe/HCl. But I have hard time to repeat the procedure. And with the extraction work up, the yield is really low.
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cactusmae
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I did use Zinc/HCl with ammonium formate at room temperature.
http://www.erowid.org/archive/rhodium/chemistry/nitro2amine....
But changed formic acid to HCl, there is no product coming out after 1 day.
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SmashGlass
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Depending on your level of resources you could try Rainey Ni in an
organic solvent (MeOH, EtOAc, ...examples) and ammonium formate or formic acid at rt.
This is a quick, cheap and relatively robust method for aromatic nitro reductions.
Without having a the structure and knowing more about your level of resources
it makes it difficult to give you a more detailed solution to your particular problem.
Good luck.
If it ain't broke don't fix it....
Now where are my screwdrivers?  |
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cactusmae
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I did try Rainey Ni once but no product. Is there any trick part for this reaction? Such as dry condition or hydrogen gas? Thanks.
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DJF90
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Raney Nickel typically requires high pressures and temperatures. Pd/C is not suitable for your substrate as you may experience hydrogenolysis of the
C-Br bonds of your protected alkene. Zn/NH4Cl(aq) is one method that works quite well to furnish the amine. If you search I'm sure you'll find a paper
on it. Not sure if it'll leave your vicinal dibromide alone though.
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