Functionalised photoswitches – photochromic dithienylcyclohexenes were prepared in two steps initiated by a cobalt-mediated Diels–Alder reaction of internal alkynes with isoprenylpinacolboronic ester.
[2+2] cycloadditions. The reactions proceed under mild conditions and provide access to differently substituted diarylethene derivatives. All the diarylcyclobutene products undergo reversible photoisomerization upon irradiation with UV/Vis light. The ring-closed isomers show different thermal stabilities towards reisomerization with half-lives ranging from 9 to 300 hours. diarylethene - photoswitchable