Epoxide Ring Opening

Ethers are generally unreactive. However, epoxides (3-membered cyclic ethers) are highly strained, so they are able to react with nucleophiles in ways a typical ether could not. Let’s take a look. 

Acid-catalyzed ring openings favor addition to the MOST substituted carbon (thermodynamic control).

  • Opening of 3-membered intermediates/molecules always results in anti-addition.

Concept: Base-Catalyzed Epoxide Ring-Opening      

5m

Base-catalyzed ring openings favor addition to the LEAST substituted carbon (kinetic control).