Dioxiranes

[Protium]

I have been reading in the literature about epoxidations with peroxymonosulfate.  In most of the articles that I am able to find, they outline creating a dioxirane in situ through the combination of oxone and a chiral ketone, which then transfers the oxygen to the substrate alkene.  In this method they state that the chiral ketone is regenerated, and thus the reaction system is made catalytic.

This raises a few questions in my mind....

1.  Has anyone used this method on isosafrole?

2.  What would be an ideal ketone to form the dioxirane for the epoxidation of isosafrole?

3.  Would creating such a catalytic system enhance the yeilds by controlling the oxidant, as opposed to simply adding the oxidant and buffering?


PS I was browsing J. Org. Chem. 2002, 67, 3479-3486

[Aurelius]

Just wanted to say thanks as aurelius had just spent some time reviewing this very area of epoxidations.  (dioxiranes, that is)  interested in the epoxidation of styrene through various methods (however, the oxone/acetone methods seem the best)

[Rhodium]

To the best of my knowledge, it has not been used on isosafrole, but I have seen it used on other styrene derivatives.

When a chiral epoxide is not the desired target compound, there is no need to use any elaborate ketone, acetone works well in most instances. However, it is not perfectly stable to oxone, and will undergo Bayer-Williger oxidation to form methyl acetate.

1,1,1-trifluoroacetone and even better 1,1,1,3,3,3-hexafluoroacetone is stable, and also more effective than standard acetone, but its higher price does not warrant its use for our purposes, unless it is carefully recycled etc, but I'd say that is too much of a hassle.

[Aurelius]

can that Baeyer-Villager oxidation be promoted and use MEK to form methyl propionate?

[Rhodium]

Yes, but you would end up with a mixture of methyl propionate and ethyl acetate, as the oxidation can take place at either side of the carbonyl.

[Aurelius]

aurelius figured that would probably happen, but that's not of any great consequence as MEK is very cheap.  (same with acetone/oxone/etc. )  thanks for the verification