Approaches to the Elucidation of the Nature of 1,4-Dehyrobenzene

Two approaches to the generation of 1,4-dehydrobenzene are described. The first, involving an attempted cycloreversion to generate initially the bicyclic form of the title compound, "butalene," gave negative results. The second approach, pyrolysis of various substituted hexene-diynes to generate substituted 1,4-dehydrobenzenes, gave evidence for the intermediacy of the 1,4-dehydrobenzene diradical in the formation of several isomerization products. A novel 1,2 silicon shift is proposed to give rise to other products through the intermediacy of substituted 1,3-dehydrobenzenes.