Electrocyclic reactions are stereospecific
Click the structures and reaction arrows in sequence to view the 3D models and animations respectively
Thermodynamically it makes sense for the four membered ring to spring open relieving ring strain. Can you explain how only one stereoisomer is obtained thermally from each ring stereoisomer, with there being no choice involved in the product?
This stereospecific behaviour is what makes electrocyclic reactions interesting; view the subsequent pages for an explanation.
Richard Windsor - Undergraduate Final Year Project 2008