|iso to MDP2P via Oxone quesitons||Bookmark|
Swim will be attempting the Oxone reaction and needs to clarify some things for his write up, he makes the following conclusions with information from the thread Post 252700 (pickler: "mdp2p from oxone", Methods Discourse)and the original, Chromicís method-oxidation of isosafrole to mdp2p using oxone
1) If the chosen route to ketone is via H2SO4 reflux, it would be preferred that only the glycol is formed rather then the epoxide?
Well, 1-alkene (safrole) to 2-alkene (isosafrole) by heat and KOH. Then we go onto the oxidation with oxone:
If it's buffered (ph near 7): the 2-alkene becomes the epoxide
If it's unbuffered: the 2-alkene becomes the glycol
Then when that's extracted and put into the H2SO4 mixture, if it's the epoxide, then it's hydrolysized to the glycol (addition of water, which opens that little epoxide ring). Then the glycol is dehydrated and rearranged by H2SO4 to the ketone by H2SO4. 2hrs of reflux (with stirring) seems to be enough time, yields have always been pretty good.
2) Since only the glycol can form the ketone, would it not be a wise move to control the Ph as to only produce the glycol? Given the epoxide must be hydrolysized to the glycol anyway.
Thermal rearrangement is heating the epoxide to about ~260C and holding for a few minutes, cranking the heat, and distilling it... it comes over somewhere around 300C (I didn't have a thermometer that went above 260C). What distills over is not epoxide, it is ketone. The crude yield is about 80%, the flask is relatively hard to clean afterwards. It has not been verified to give a good purity, but I know it works, and I think the purity is decent.
3) As an alternative to H2SO4 reflux, which according to some posts is not very efficient, would the above method be preferred if the epoxide was produced rather then the glycol?
SWIM is somewhat confused about the middle of this procedure because the oxidation of 2-Alkene with Oxone yields two products, glycol and epoxide. Both of the products in the end make it to ketone however is seems by different methods (Thermal rearrangement or H2SO4 reflux). He is curious to see which method is more efficient/preferred.
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As far as I'm aware of the glycol will rearrange to the ketone at high temperatures as well. I much prefer the H2SO4 rearrangement, and would use the p-tosic acid rearrangement if I could find a way to form it more easily.
Forming the glycol or the epoxide doesn't really matter. I'd try for the epoxide if you're going for the rearrangement tho.
If you are to try a thermal rearrangement. first distill the oil under vacumme then thermaly rearrange each fraction seperatly.
With the H2SO4 rearrangement i have found that 3 hrs is nescesary for optimal yeilds with good stirring.
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