Catalysts achieve regioselectivity through several mechanisms:
1. Steric Effects: Catalysts can impose steric hindrance, making certain positions on the substrate less accessible and thus directing the reaction to more accessible sites. 2. Electronic Effects: Catalysts can alter the electron density distribution in the substrate, making certain positions more reactive. 3. Template Effects: Some catalysts provide a template that holds the substrate in a specific orientation, ensuring that the reaction occurs at the desired position.