feynmann
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orthanilamide
Well i will start with what is done
1-Starting with 2-nitroaniline as cheap and available raw material ,I converted it to 2-nitrobenzenesulfonyl chloride using the method of diazonium
salt formation followed by its addition to a saturated solution of sulfur dioxide in glacial acetic acid.
2-2-nitrobenzenesulfonyl chloride was converted to 2-nitrobenzenesulfonamide by adding to conc solution of ammonia and heating
3-The remaining step is the reduction of nitro group
I carried it using many methods
1-Using Hydroiodic acid (but realized it's more expensive than the final compound itself )
2-Using hydrazine and nickel (Hydrazine become watched now in our country)
3-Using SnCl2 and absolute ethanol .........good but needs much time in the workup as adding NaHCO3 in the workup will lead to the formation of
insoluble form of the salt and therefore needs extraction with ethylacetate
The point is:
I need a method to reduce the nitro group without need for any extraction in workup (No solvent requirement)
So I thought about sodium dithionite as it works well in water and alkaline medium (I can use the ammonia in the previous step)
The question is
Is it good here to use dithionite...I am asking if it supposed to give byproducts ?
Here is a possible scenario for the procedure (plz give ur comments on it if there is something illogic or wrong)
-suspending the cpd in water and add ammonia or 1N NaOH
-add sodium dithionite slowly ,stirr
-Reflux (can anyone guess what should happen ? i know that the cpds are soluble in hot water so it is logic to dissolve)
-FIlter while hot to remove undissolved substances
-add acetic acid to neutralize and cool ..it should seperate(it may need to concentrate the solution though before cooling)
(I know some will comment why I don't try it ....Cause I don't have dithionite at the moment and will need to buy so I am asking for ur suggestions if
u plz_and I promise I will make detailed procedure work out for this cpd
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Nicodem
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Have you tried hydrogenating with Pd-C (5%)? That is the only way to make the work up easy and yield quantitative, since it only takes to filter off
the catalyst and rotavap. You might be worried about catalyst poisoning, but as far as I know sulfamides do not poison Pd. I might be wrong though,
but it is worth trying. If no poisoning occurs, most nitroaromatics can be reduced to amines with Pd-C load as low as 0.1-1 mol% at 60 PSI hydrogen.
Sodium dithionite should work, however you will never reach near quantitative yields since o-aminobenzenesulfamide should be quite soluble even in
cold water (you should check). I don't understand why would you want to neutralize with acetic acid in your proposed workup. Also, with reductions
with Na2S2O4 it is Na2CO3 that is used to maintain the reaction medium basic. I don't think using NaOH is a good idea. The reduction can also proceed
even without the carbonate and the remaining NH3/NH4Cl buffer might already be enough. In short, you must try it and see.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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smuv
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I have experience with the SnCl2 reduction (on a different substrate); I did not have any problems with work-up on a small scale; you could add oxalic
acid to precipitate the tin (i assume stannic and stannous oxalates are insoluble in EtOH/H2O mixtures). I did not get good yields with the
reduction, but that was because I had to use a lot of solvent as my substrate was very insol in alcohol and had 2 nitro groups (on different rings).
You might also want to look into the zinin reduction; it is very mild, although I cant recall how ortho EWG's affect the reduction.
C. Niu et al. /Tetrahedron 54 (1998) 6311-6318
P.S. Does anyone have a ref for the dithionite reduction; I have never seen a literature example where the reduction did not use an electron carrier
as a catalyst.
[Edited on 2-13-2009 by smuv]
"Titanium tetrachloride…You sly temptress." --Walter Bishop
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feynmann
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| Quote: | Originally posted by Nicodem
Have you tried hydrogenating with Pd-C (5%)? That is the only way to make the work up easy and yield quantitative, since it only takes to filter off
the catalyst and rotavap. You might be worried about catalyst poisoning, but as far as I know sulfamides do not poison Pd. I might be wrong though,
but it is worth trying. If no poisoning occurs, most nitroaromatics can be reduced to amines with Pd-C load as low as 0.1-1 mol% at 60 PSI hydrogen.
Sodium dithionite should work, however you will never reach near quantitative yields since o-aminobenzenesulfamide should be quite soluble even in
cold water (you should check). I don't understand why would you want to neutralize with acetic acid in your proposed workup. Also, with reductions
with Na2S2O4 it is Na2CO3 that is used to maintain the reaction medium basic. I don't think using NaOH is a good idea. The reduction can also proceed
even without the carbonate and the remaining NH3/NH4Cl buffer might already be enough. In short, you must try it and see. |
Thanks Nicoderm for ur concern
Here are my comments:
1-Pd/C works fine :
I use it to reduce 2-amino-5-nitrobenzenesulfonamide and gave almost quantitative yield .
2-Dithionite
I saw many procedures where ammonia is utilized
an example is:
http://www.orgsyn.org/orgsyn/prep.asp?prep=cv3p0069
I could see in this procedure that the author neutralized the solution using acetic acid ..that is why I suggested adding it ...I know I may be wrong
though
3-I know that orthanilamide has certain solubility in water
0.65g per 100gm at 23oC and about 2 gm/100gm at 50oC
but I don't really know what this should do with the reduction
I think it is not highly soluble in water .
In addition if it is soluble in water ...what should this do with the yield ??I really don't know
4-I will post some examples of dithionite procedures
5-Sncl2 requires addition of NaHCO3 that precipitates it
so that u will have to extract the product using ethyl acetate or any other suitable solvent and that what I want to avoid :extraction
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feynmann
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Verwendnng von Natriamhydrosnlfit als Reduktionsmittel fur organische Snbstanzen;
This paper is good
Attachment: sodium dithionite.pdf (879kB)
This file has been downloaded 739 times
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feynmann
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WEYGAND/HILGETAG
PREPARATIVE ORGANIC CHEMISTRY
p 562
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Nicodem
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I was not aware of ammonia or amines being used as a base in reductions with Na2S2O4, but then again I only used this reagent a couple of times. I
always only saw Na2CO3 being used, so thanks for sharing these examples.
I think the reaction mixture is neutralized, in the Org. Synth. example, because they were reducing a 1,4-phthalazinedione which are weak acids and
are probably more soluble in aq. ammonia than in neutral. Since your sulfamide is not particularly acidic, you don't have to worry about this. Also,
the aq. solubility of the product is low enough for actually precipitating efficiently from the reaction mixture upon cooling just like in the Org.
Synth. example. I expected it would be more soluble.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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feynmann
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Thanks Nicoderm once more for ur prompt response ..
Here is the paper which discuss the solubility of some sulfonamides for anyone who wants further reference
Attachment: Solubilities of Orthanilamide, Metanilamide and Sulfanilamide.pdf (473kB)
This file has been downloaded 690 times
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