[ohmahon0903]

I'm working on a research paper involving the Jacobsen Epoxidation. My professor's feedback on my first draft included explaining (more thoroughly) WHY the reaction is enantiomerically pure (~95%).


I guess I just don't really understand how to explain this, or don't entirely understand it myself- here's what I'm trying to understand and formulate:
I understand that converting the starting product to an ending product with the conformation of S,S (in this case) takes less energy to the minimal rearrangement, but why is it in such high purity whereas often times you get a racemic mixture of both enantiomers?


I'd really appreciate some input on this. My TA wasn't quite sure how to explain it so I'm hoping you guys can help out! Thanks!

[discodermolide]

Have a look here:
http://www.chem.harvard.edu/groups/myers/handouts/18_Jacobsen_Asymmetric.pdf

[ohmahon0903]

I've had that handout on record, but thank you.
My question is more of WHY the enantioselectivity is so specific, not how, as the handout explains. Does that make sense?

[Dan]

You need to draw model transition states and show that the energetic path to one enantiomer is significantly more demanding that the other.

Check the literature, stereochemical models will have been drawn before.