reduction dominantly occurs over the acetylene reduction. The produced bis(radicalanion) intermediate undergoes a synchronous double-radical 5-endo-dig cyclization. This simple reduction procedure produces two intriguing classes of ladder π-conjugated skeletons, i.e., emissive methylene-bridged stilbenes and dibenzo[a,e]pentalenes regarded as a cyclic 1,4-diphenylbutadiene.