The most common example is E-stilbene, which upon irradiation undergoes an E to Z isomerization, which can be followed by a 6π electrocyclization.
In the original 1952 publication, additional evidence was obtained for the structural assignment of the reaction products by applying them to a Chugaev elimination, wherein the threo isomer reacts to the cis isomer of -α-methyl-stilbene and the erythro isomer to the trans version.