Hello. I have been reviewing the data on the catalyzed rearrangement of our favorite epoxides to our favorite ketones. The subject at this time: Rearrangement with Lithium Iodide, (LiI). In several papers, The general procedure for the reaction is to take the epoxide of safrole or isosafrole, allylbenzene or propenylbenzene (explanation in a second) and react it with Lithium Iodide, causing it to rearrange itself to the corresponding ketone: MD-P2P, or P2P, respectively. Now I have a few questions on these procedures that I dont understand:
All of the following information was gleaned from Rhodium's site.
First off, according to the procedure in the last entry of
https://www.thevespiary.org/rhodium/Rhodium/chemistry/phenylacetone.html
, entitled Phenyl-2-Propanone (very last entry), and I quote: "12g of 1-Phenyl-1,2-epoxypropane (propenylbenzene epoxide) was dissolved in 18 ml of tetraglyme and treated with anhydrous LiI..." For this reference, it specifically cites the usage of the 1,2-epoxypropane, corresponding to the epoxide of the propenylbenzene.
However, another reference,
https://www.thevespiary.org/rhodium/Rhodium/chemistry/peroxotungstate.html
, on the pertungstate epoxidation, explicitly shows the epoxide in the 2,3 configuration, corresponding to the allylbenzene. Both references state that upon addition of anhydrous LiI, these isomeric epoxides both rearrange to the same ketone (2-Propanone).
My question is very specific here: Does it matter which epoxide is used, the propenyl or allyl, for the rearrangement with LiI to the 2-Propanone?
Next question: Both of the aforementioned references state that the epoxides were dissolved in
tetraglyme. Chemfinder states: Tetraglyme = Synonyms: 2,5,8,11,14-Pentaoxapentadecane; Tetraglyme; Bis[2-(2-methoxyethoxy)ethyl] ether; Dimethoxy tetraglycol. Well, its B.P. is very nicely high and all, but its hygroscopic and sensitive to air, too. Not too great. The LiI is anhydrous. Not good to couple that with a hygroscopic solvent. I dont know how to make it, nor do I want to buy it.
The third reference I looked at for this reaction,
https://www.thevespiary.org/rhodium/Rhodium/chemistry/uspat4731482.html
, see example one: MD-P2P, the procedure makes no mention of tetraglyme. This gives me hope.
Is tetraglyme necessary for the reaction to occur? Could something like a nonpolar, or ether, or an alcohol, be substituted for it? If you know which and which not, please be specific.
Also, in case anyone still thinks tetraglyme is a good solvent, note that chemfinder states its flashpoint at 116°C, but the reaction is carried out at 130°C for 5 hours.
Next question: Can NaI be substituted for LiI? If not o well, but its worth a shot at asking. I can always toss battery powder on some iodine....
(no Im not that stupid)
Well, thank you for any information you decide to tell me. I really think this is a neat alternative to the glycolysis with nasty H2SO4, but hasnt really gotten too much interest. Id like to find all this out, so maybe my future dreams will include its synthesis and a writeup. Thank you.
PrimoPyro
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