03-22-03 22:35
No 420370
I had been reading some journal articles on the use of Oxone and dimethyldioxirane for the purpose of oxidating alkenes, and I was wondering why the DMDO reactions are always carried out in acetone as the solvent? Would it be possible to use a small amount of acetone dissolved in water or an alcohol to carry out the oxidation? I'm under the impression that DMDO reduces back to acetone after it oxidizes something, so could you use the acetone as a form of catalyst? It would be nice if you could use smaller volumes of solvent and process larger volumes of alkenes without having to worry about having too strong of a molar concentration of DMDO.
If DMDO is not soluble in water or alcohol, I guess this is out of the question. I haven't found much on it's solubilities yet.
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(Chief Bee)
03-23-03 11:45
No 420547
You don't have to worry that much about DMDO as long as it is in a dilute solution. It is only really unstable when pure.
(Hive Addict)
03-23-03 12:17
No 420560
I'm under the impression that DMDO reduces back to acetone after it oxidizes something, so could you use the acetone as a form of catalyst?
Oxone oxidizes acetone to dimethyldioxirane. The latter is reduced back to acetone when it has epoxidized an alkene. You are not obliged to choose for acetone, other ketones can work as well. For instance: Wang et al., An efficient catalytic asymmetric epoxidation method. JACS 119 (1997) 11224-11235. They developed a ketone, based on fructose, which catalyzes the epoxidation of the alkene by oxone.
This group has written several articles using the same catalyst over and over again (you can say they milked it out pretty well), studying the effect of solvents, pH etc. In their case, MeCN seemed to be a good solution. Also keep in mind the pH of your reaction mixture. The oxirane ring of our phenylpropane epoxides is very often pH sensitive. Several articles covering that subject as well.
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(Stranger)
10-10-03 10:58
No 463818
Just bringing an old thread back to life!
For what is worth, DMDO epoxidations are only worth doing on a very small scale. Hundred of grams of oxone are required to generate even ~20ml of 0.07M DMDO in acetone. It is of course a fantastic method, since you stir for several minutes and then vac off all volatiles to leave pure epoxide product. It is however, not really practicable on a >1g scale.
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