text: Quite parallel to the santonin to lumisantonin example is the rearrangement of 4,4-diphenylcyclohexadienone<Ref Name=Schuster2/> Here the n-pi* triplet excited state undergoes the same beta-beta bonding. This is followed by intersystem crossing (i.e. ISC) to form the singlet ground state which is seen to be a zwitterion. The final step is the rearrangement to the bicyclic photoproduct. The reaction is termed the type A cyclohexadienone rearrangement.