Scheme 2. The Two Mechanisms Explored, A and B, for the Photorearrangement of Benzene in Nucleophilic Media (here MeOH) Leading to 4-Methoxy-bicyclo[3.1.0]hex-2-ene (1).

Note that benzene in the T₁ state can act as a triplet sensitizer of benzvalene 4, which ring-opens to the S₀ state of benzene.