Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: meaningfulgibberish on July 23, 2015, 01:21:58 PM
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I've been running this reaction for a couple months now. I take N,O-dimethylhydroxylamine salt, add to it either DIBAL or Trimethylaluminum, then add that solution to a solution of a lactone. Work-up consist of quenching any small amount of DIBAL left, acidification to pH 3-4, then overnight stir in Potassium Sodium Tartrate. Previous grad student would typically get anywhere from 30%-40%. I'm at best getting 20%.
Does anyone have any experiences with these reactions? What are some things I could do to improve yield? I know synthesis can be frustrating but this is beginning to be ridiculous.
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What is the rest of the material? Starting material or what?
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At times I'll get a small amount of starting material back, but the mass balance wouldn't make sense if it was a conversion problem. I'm not getting enough starting material back to say that it is a conversion problem. My other guess is that my product may still be stuck on the aluminum. It would explain the drop in yield when I'm using tartrate in my work-up. But then if that's the case, why is it still on there?
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Try using acetic acid quenches. But be careful, keep it controlled. The Rochelle salt may not be enough to remove all the Al, I have had better results, in different systems, with acetic acid.
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I'll give it a shot. Thanks!
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What to you have planned for the Weinreb amide product? I ask because morpholine might be a better choice, see:
http://www.sciencedirect.com/science/article/pii/S0040402014003792
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What to you have planned for the Weinreb amide product? I ask because morpholine might be a better choice, see:
http://www.sciencedirect.com/science/article/pii/S0040402014003792
This looks great! I use the weinreb amide to make a ketone. The grignard addition works fine, but this looks like a much better alternative. Thank you!