A versatile scheme for the synthesis of geminally disubstituted cyclopentadienes is used to prepare the title compound 4. This remarkably stable vinyl‐cyclopentadiene, distinguished by its Cs symmetry, undergoes exclusively electrocyclic ring closure upon direct π–π* excitation at 254 nm. The epimeric vinyl‐housenes 11 and 12, which, for geometric reasons, are insensitive to the walk rearrangement, are suggested to be the primary photo‐products. One of them, 12, due to its syn‐oriented vinyl group, undergoes spontaneous copy rearrangement to give 2‐methylbicyclo[3.2.1]hepta‐2,6‐diene (13). The other, 11, having an anti‐oriented vinyl group, can only undergo thermal return to the starting material 4. Whereas no leakage to a 1,5‐vinyl migration is discernible for the S1 state of 4, the benzophenone‐sensitized photolysis at 350 nm is shown to be governed by this rearrangement. 1‐Methyl‐5‐vinylcyclopenta‐1,3‐diene (14), the unstable primary product of the sensitized photoreaction, is trapped by 4‐phenyl‐3H‐1,2,4‐triazole‐3,5(4H)‐dione (PTAD).
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