Photochemical conversion of poly 2,3-diphenylbutadiene

During UV irradiation (313nm) of poly(2,3-diphenylbutadiene) (3.111) in dichloromethane (CH2CI2) solution, two types of photoreactions occur [1046]  

Cyclization of pendant phenyl groups to dihydrophenanthrene (3.112) (this reaction dominates over isomerization)  

In the dark and in the absence of oxygen, dihydrophenanthrene groups undergo a reverse reaction to the initial state  

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