2,3-sigmatropic rearrangement

[1] The general scheme for this kind of rearrangement is: Atom Y may be sulfur, selenium, or nitrogen.

If Y is sulfur, the product can be treated with a thiophil to generate an allylic alcohol in what is known as the Mislow–Evans rearrangement.

At the newly formed double bond there is a strong preference for formation of the E-alkene or trans isomer product.

Diastereoselectivity can be high for Z-alkene with alkynyl, alkenyl, or aryl anion-stabilizing group.

Hydrocarbon groups will prefer exo orientation in the envelope-like transition state.