As part of my PhD project, I'm currently looking into running a Shi Epoxidation reaction. The first step is to reproduce the current literature on this reaction by using trans-stilbene as my substrate. However, from the multitude of reaction conditions I have tried, none of them seem to work as described in the papers (very low to no conversion observed). I have tried the reaction conditions from the following papers:

  1. "An Efficient Asymmetric Epoxidation Method for trans-Olefins Mediated by a Fructose-Derived Ketone" - the original Shi paper - using oxone as oxidant
  2. "An Efficient Catalytic Asymmetric Epoxidation Method" - Shi - optimized conditions - using oxone as oxidant
  3. "Asymmetric epoxidation using hydrogen peroxide ($\ce{H2O2}$) as primary oxidant" - Shi - using hydrogen peroxide as oxidant

The catalyst I have used in my reactions is the Shi Diketal Catalyst purchased from Sigma (https://www.sigmaaldrich.com/catalog/product/aldrich/520160?lang=en&region=CA). What I've tried so far:

  1. testing different batches of oxone, including titrating it and running test reactions ($\ce{aldehyde -> COOH}$ oxidation) - > 90% conversion observed
  2. trans-stilbene + m-CPBA -> oxidized product is quantitative
  3. I've left reactions run for > $\pu{6-24 h}$ with low conversion observed (< 30%).
  4. $\mathrm{^{13}C}$ and $\mathrm{^{1}H}$ NMR of the catalyst show that it's clean

I am slowly running out of things to try out. It's weird because it's a published and highly used reaction ... If you have any experience with this reaction I would really appreciate your help!

  • 1
    $\begingroup$ What pH are you running your reactions at? $\endgroup$ – Waylander Aug 20 '19 at 9:20
  • 1
    $\begingroup$ Please add proper citations to the papers so that they are easier to find. $\endgroup$ – Martin - マーチン Aug 20 '19 at 14:01

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.