Diphenyl ditelluride 2 has been found to add efficiently to various acetylenes 1 upon irradiation with visible light (>400 nm), providing vic-bis(phenyltelluro)alkenes 3 in good yields.
stereoselectively to provide only (E)-vic-bis(phenyltelluro)alkenes. Contrary to this, activated acetylenes like phenylacetylene give rise to a mixture of E- and Z-isomers of vic-bis(phenyltelluro)alkenes. Since the obtained vic-bis(phenyltelluro)alkenes indicate absorption in the near-UV, irradiation with near-UV light in solvent causes a novel reverse reaction of the adducts to the starting acetylenes and diphenyl