Epoxide Opening to Give Chair Conformation

Picture displaying epoxide opening to give chair conformation

Click the structures and reaction arrows in sequence to view the 3D models and animations respectively

The phenyl group locks the conformation of epoxide since it stays equatorial, so there is only one conformation in each of the two isomers. The azide (N3-) nucleophile must attack the epoxide from behind in order to interact with the C-O σ* orbital. This means that the nucleophile and the epoxide oxygen will always be trans in the product. In the cases above, the ring opens out to give a diaxial chair conformation product. Although the two groups are axial, the chair conformation is stable.

Nucleophilic attack at the other carbon would give a diaxial twist boat conformation, which could twist to give a fully equatorial chair product, but the kinetic barrier to forming the high energy, diaxial twist boat intermediate is too high for this to happen.

A. Solladié-Cavallo, J. Suffert, A. Adib and G. Solladié, Tetrahedron Lett., 1990, 31, 6649–6652.

()

How useful was this page?

Click on a star to rate it!

Average rating / 5. Vote count:

No votes so far! Be the first to rate this page.

As you found this page useful...

Follow us on social media!

We are sorry that this page was not useful for you!

Let us improve this page!

Tell us how we can improve this page (in your own language if you prefer)? If you would like a response, please include your email address e.g. [email protected]

Provided by the