How to determine whether to use heat (A) or light hx) in an electrocyclic ring opening?

How to determine whether to use heat (A) or light hx) in an electrocyclic ring opening?
How to determine whether to use heat (A) or light hx) in an electrocyclic ring opening?

I’m far from being an O-chem maven. But maybe this will help? bit.ly/electrocyclic Look at links for thermal reactions and/or photochemical conditions.