I did the reaction shown in the image attached to this question, reported in the article with DOI: 10.1021/jm900431g
I need the first product (the ortho-nitro substituted one), but I have always the 30% of the second product, and I'm not able to purify them.
The article reported the purification by cristallization with methanol, but I tried and I found always 10-20% of subproduct.
I tried also a flash cromatopraphy with different eluent (Hexan/EtOAc, Hexan/Methanol, Toluen, Toluen/Methanol, Toluen/Et2O), but the pollution still in the fraction.
Can you help me with other ideas?
Flash chromatography is best technique, but be careful about amount of the sample and size ( length and diameter ) of the funnel and quantity of used silica (60 H).
Good morning to all.
I'm of the opinion that the two compounds cannot be easily separated with column chromatography since the separation by this technique is obtained mostly on the base of polarity and the two compounds have virtually the same polarity being isomers. It is also true that a portion of the loaded sample is lost in column so repeating the chromatograpic run a number of time the minor component will disappear in the end. Obviously this led also to loose a portion of the product of interest.
For what concern the crystallization method, this should be repeated a number of time to obtain an adequately pure sample.
Hello depending of the scale I guess, if small C18 prep HPLC could be an option. You can also run C18 column like silica. When it comes to silica, often the trick if also in running a very slow gradient and slow flow rate. Next is the solvent system... many to try, with 2 or even 5 solvents... :)
Preparative HPLC (or semi) with a C18 or Phenyl-hexyl. You will not be able to separate isomers with collumn chromatography.
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