Naturalproductman’s Blog

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Removing triphenylphosphine oxide

Posted by naturalproductman on May 14, 2013

I have had this silly problem in trying to get rid of triphenylphosphine oxide from my reaction mixture.  It’s stuck with my final product and can be a pain.  Some tricks I’ve seen are the use of dissolving mixture (O=PPh3 and product) in ether and run through short pad of silica.  This would be great if my product weren’t so polar – instead my product does not elute with ether.  Another trick was from this Lipshutz paper in 2003 where they used Merrifield resin to scavenge the phosphine.

 

OL paper

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9 Responses to “Removing triphenylphosphine oxide”

  1. Brad said

    You can also complex with ZnCl2 in Et2O and decant/filter

  2. Professor Tom said

    I recall a similar problem a long time ago with a polar compound and the solution was a column with acetone in methylene chloride, 3% or 5%. It’s an odd mix, and acetone absorbs in the UV so an automated column like Biotage or Isco isn’t the way to go unless you ignore the detector, but that system does well with polar stuff, better than methanol or ethanol in DCM.

  3. naturalproductman said

    The ZnCl2 reaction can be complicated if there are other functional groups present. I allude to this TL paper (http://www.sciencedirect.com/science/article/pii/S0040403997829528 Volume 37, Issue 52, 23 December 1996, Pages 9317–9320).

    I think reasonable alternatives to triphenylphosphine could be the water soluble TPPTS (Tris(3-sulfophenyl)phosphine trisodium salt) as a ligand.

    • naturalproductman said

      I like the Merrifield resin idea because in the paper it even says: “Reaction products bearing most functional groups, including free amines and alcohols (e.g., benzyl alcohol), are unaffected.”

  4. milkshake said

    PPh3O has a fairly limited solubility in benzene or toluene. If your crude product dissolves in benzene I would let it sit for a day and hope that most PPh3O would gradually crystallize out. Of couse this works even better if you can dilute your benzene solution with some cyclohexane (up to equal volume) without precipitating your product

    • Fenton Heirtzler said

      Hey Milkshake,

      Your response to the TPPO question leads me to ask another question. I am carrying out an Appel reaction, using CCl4 and Ph3P. Do you know of any other easy means of carrying out this conversion? SOCl2 won’t work, because the starting material is acid-sensitive.
      Thanks
      Fenton

      • milkshake said

        you can use SOCl2 (2 equivs) with pyridine-DCM as a solvent. Or you can make mesyl derivative (MsCl, NEt3, 0C), isolate the crude mesylate and treat it with anhydrous LiCl (large excess) in DMF

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