Abstract 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 C s 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 ...
