I have reduced a nitro to amine using SnCl2 under acidic conditions, neutralized the solution using NaOH and precipitated Sn(OH)2 and crystallized a product (amino acid) from aqueous solution using AcOH. Normally this reaction gives good yields but this time the yields are very low (less than 20%). Could this be the work up procedure (co-precipitation) or scale of crystallization...any ideas?
Most likely yes. I would suggest you adjust the pH to neutral and avoid to add water as Zwitterionic compounds are often quite water soluble. As a work-up, you can try to add potassium fluoride in excess and filter the tin-fluoride complexes. Tin is fluorophilic and tends to form ionic salts (a bit like silicon does with higher silicates...). Those are not soluble in most organic solvents.
Thanks Pierre-André Fournier, I'll give it a try and I have also found additional sources confirming your answer..... D. Tudela, F. Rey, Z. Anorg. Allgem. Chem. 575 (1989) 202; D. Tudela, J.A. Patron, Inorg. Synth. 31 (1997) 92...Thanks a lot..
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