[StarvinMarvin]

Guys, now I have a problem. Here's the thing:

I am trying to oxidize an amine (it's a glucosamine) to a nitro group with m-CPBA. The reaction works fine, but the workup is just a nightmare. According to the procedure I've got, reaction mixture needs to be diluted with DCM (reaction done in CHCl3) and extracted with 0.1 M NaOH and water. And here's the problem: Maybe on paper it works well, but basic workup does not work on the benzoic acid which I need to get rid of. Even after recrystallization from EtOH, I've got lots of benzoic acid in the NMR. I also tried first to evaporate chloroform and dissolve the benzoic acid in NaHCO3 and then extract it with DCM. Still, benzoic acid remains in the product. I ran out of ideas, so maybe you can help.

[orgopete]

I think you have residual mCPBA present. You didn't report the pH of the washes. Because mCPBA is a weaker acid, it doesn't ionize with NaHCO3. I would change the work up to reduce the mCPBA to m-chlorobenzoic acid (but not your nitro group) and then NaHCO3 should work.

[408]

Why not try a cleaner oxidant like ozone?

[StarvinMarvin]

Why not try a cleaner oxidant like ozone?

The thing is, that I need a selective oxidant. Secondly, the reaction works, it's published, but the guys from the paper put only a general procedure which is full of inconsistencies. Following their procedure to the letter results in impure product.

I think you have residual mCPBA present. You didn't report the pH of the washes. Because mCPBA is a weaker acid, it doesn't ionize with NaHCO3. I would change the work up to reduce the mCPBA to m-chlorobenzoic acid (but not your nitro group) and then NaHCO3 should work.

I can't think of any reducing agent mild enough that it would not decompose the product at the same time
The washes are basic. I think m-CPBA and its reduced counterpart are not that prone to go into the aqueous layer.

[gfunk]

Maybe try contacting the author about their workup procedure?  How about a good ol' column?   Perhaps, with alumina?

[StarvinMarvin]

I actually wrote the guy and now all I have to do is wait. Hopefully, they would shed some light on it. But I already have some feeling that something's terribly wrong here. I mean, if you put general procedures, there can be a reason for not revealing every aspect of making each model (I think I'm going bananas because I sniff conspiracies everywhere)

Column you say? I have to think about it but I'm affraid it would decompose. (anyway, maybe it will eventually come down to a column and crossing fingers)  

[orgopete]

I can't think of any reducing agent mild enough that it would not decompose the product at the same time

You could give us your compound, but I will give it a try anyway. Cyclohexene, ammonia, thiosulfate, hydroquinone, dimethylsulfide, an aldehyde. So these all decompose your product?

mCPBA is not that water soluble, but the salt of it will be more water soluble. mCBA as its salt is a lot more water soluble. Did you test your organic for the presence of peroxides? I am guessing it has peroxides present. I think that is the reason you are seeing the impurities and not because mCBA is difficult to remove.

[gfunk]

I actually wrote the guy and now all I have to do is wait. Hopefully, they would shed some light on it. But I already have some feeling that something's terribly wrong here. I mean, if you put general procedures, there can be a reason for not revealing every aspect of making each model (I think I'm going bananas because I sniff conspiracies everywhere)

Column you say? I have to think about it but I'm affraid it would decompose. (anyway, maybe it will eventually come down to a column and crossing fingers)  

Usually one does not go into great detail in workup procedures in a paper.  But if an experiment can't be replicated by others, then it's kinda fishy!

Anyhow, running a silica column might cause side reactions.  I've seen reactions in schemes whereby running the reactant through the column affords the product lol.  But, alumina is slightly basic, just like your wash conditions.  So hopefully that won't mess around with your product, and those acid/base interactions might help with the separation.