Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: wisconsinium on May 31, 2012, 12:58:45 PM
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I have tried using DDQ to aromatize a compound and the work up was a disaster. I'd appreciate any tips about safety and work up with this material from someone who has used it. I used 1.1 equivalents and refluxed with my starting material in dry dioxane. Should I quench the reaction with aqueous sodium bisulfite or is that not necessary? Is there really such a big risk or cyanide formation?
What color is DDQ-H? I can't find any references about it. Anyway, I added water and got a red precipitate. My compound is new but I am expecting it to be colored and also insoluble in some solvents. I filtered and rinsed with aq bicarb, thinking any DDQ-H would rinse out and got a bright yellow filtrate and the red stuff remained. So could the red solid be my product or is it trapped in the red stuff which is the DDQ-H? I tried to take an NMR of the red solid and it was too messy to be helpful.
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I have tried using DDQ to aromatize a compound and the work up was a disaster. I'd appreciate any tips about safety and work up with this material from someone who has used it. I used 1.1 equivalents and refluxed with my starting material in dry dioxane. Should I quench the reaction with aqueous sodium bisulfite or is that not necessary? Is there really such a big risk or cyanide formation?
What color is DDQ-H? I can't find any references about it. Anyway, I added water and got a red precipitate. My compound is new but I am expecting it to be colored and also insoluble in some solvents. I filtered and rinsed with aq bicarb, thinking any DDQ-H would rinse out and got a bright yellow filtrate and the red stuff remained. So could the red solid be my product or is it trapped in the red stuff which is the DDQ-H? I tried to take an NMR of the red solid and it was too messy to be helpful.
We used DDq many times. It looks like a messy reaction but it's not really. The conditions depend a lot upon your substrate, some use buffered conditions, some not. Usually one uses Mol. sieve to keep it dry. I have attached an experimental procedure that we used. It may be of use.
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So is there a typical color after the reaction is over and the DDQ forms the hydroquinone?
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Washing your product solution with 1N NaOH removes most of the DDQ-H.
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Washing your product solution with 1N NaOH removes most of the DDQ-H.
That is in the procedure I uploaded!
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Sorry disco...too lazy to read :D
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Sorry disco...too lazy to read :D
LOL, shame on you, that was (is) one of my procedures and it works. :o
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OT on: Yeah but your procedure is no myth to the experienced chemist ;D
Have done it accordingly on *only* 500g scale. But with better yield (*ducking down*).
OT off.
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OT on: Yeah but your procedure is no myth to the experienced chemist ;D
Have done it accordingly on *only* 500g scale. But with better yield (*ducking down*).
OT off.
There is a good chance that my yield may be somewhat more reproducible and anyway it is easy to get better yields than that quoted here when employing simple molecules ;D