Bases of amine group purification via sodium bisulfite adduct

[Mr Good Cat]

I saw recently a discussion in some RC community saying about amph group and 4mmc purification via bisulfite adduct.

Considering molar proportions, mentioned there, I don't think this route was developed by a professional. But I brought it here to discuss: may be it worth to pay attention on it.

Briefly, it is described in following steps:

1. Base extracted with NaOH and separated with solvent (DCM, hexane, etc).
2. Sodium bisulfite NaHSO3 water solution added in huge molar proportions 1:4 or even 1:5 (where 1 is base and 4 is bisulfite) to the base dissolved in solvent.
3. Bisulfite adduct precipitates immediately and washed with extra solvent
4. Washed bisulfite adduct turned back to the base via addition of carbonate sodium Na2CO3 in the same huge molar proportions 1:4.
5. Base separated
6. Job done

Said, this route is suitable for meth and amph group, as well as 4mmc.

I understand the principle: sodium bisulfite has weak acidic properties, and may turn some bases to a sodium adduct, that obviously precipitates in such solvents as DCM, ether, hexane and water. But I haven't found any well known protocol for such sodium bisulfite usage.

Abeit, there are a few well known protocols when this route (with different solvents) of sodium adduct formation is used in pharmacy manufacturing, but generally for ketones purification.

Any opinion from experts about this route?

 

[Frit Buchner]

I'm not an expert or even an avid ameteur but I would suspect that the person who wrote this isn't either. As far as I can tell the sulfite cation is the conjugate base of the conjugate base of sulfuric acid. To me I think that means it won't form a Lewis acid with much. Metals.
Maybe I'm completely off base. You asked me to comment so I spent about 30 minutes looking at the genetics involved and I don't see it being viable

 

[Mr Good Cat]

Yes, I also read more on this topic and tried to understand it. It looks, at least as it introduced here, it is totally senseless.

 

[Frit Buchner]

Actually I think I got it. What you are referring to seems to be adding sodium bisulfite specifically to an aldehyde to make a sulfonate. That is a well known reaction that fits well with what you are proposing and works. Many aldehydes become drugs and a sulfonate sounds like a Lewis acid to me

 

[Mr Good Cat]

Actually I think I got it. What you are referring to seems to be adding sodium bisulfite specifically to an aldehyde to make a sulfonate. That is a well known reaction that fits well with what you are proposing and works. Many aldehydes become drugs and a sulfonate sounds like a Lewis acid to me

Frit BuchnerBut any way, sodium bisulfite reacts with both, amines and ketones. And probably, other organic compounds (impurities) as well. We turn all of them to bisulfite adducts, then turn them back to the former stage. So, it looks as useless if we are targeting to separate organic compounds.
But for inorganic compounds it will work well. But again, base extraction is enough for that.

 

[2-79-790125]

Seems like a logical place to post my question........

I need to test for successful MDP2P synthesis from a Wacker Oxidation of Safrole, Benzoquinone, Palladium Chloride (Bright Star's recipe backed up by Strike's Total Synthesis II, Methylman's and Dr. Drool's modifications, and probably a dozen other resources)
This was my first attempt and resulted in a pathetically low yield so I haven't even bothered with the last step of slowly distilling the solvent off the MDP2P. It's sitting in the freezer.

First question - do we all agree that dripping MDP2P in a saturated sodium bisulfite solution will cause a precipitate?
question #2 - would that same precipitate potentially appear if dripping in MDP2P still mixed in with the RM (reaction mixture) solvent or it is critical to isolate the MDP2P from the solvent first?
Question #3 - any tips on preparing a saturated sodium bisulfite solution?
Question #4 - which is easier to isolate/purify MDP2P? distilling solvent to isolate the MDP2P vs. adding all the MDP2P/solvent mixture to saturated sodium bisulfite then filtering out the MDP2P precipitate