A Simple Route to cis- and trans-Bis-σ-homobenzenes

Photolysis of tetracyclic azo compounds 15, readily available from [4+2] cycloaddition between 1,2,4,5-tetrazines and cyclopropenes, gives access to cis- and trans-bis-σ-homobenzenes 16 and 17. Thermal transformation of the cis isomers 16 affords cis,cis,cis-1,3,6-cyclooctatrienes 18. Kinetic data for these [σ2s+σ2s+π2s] cycloreversions are reported.