ADDITION-REACTION OF POLYCHLORO COMPOUNDS TO CARBON-CARBON MULTIPLE BONDS CATALYZED BY SEMICONDUCTOR PARTICLES UNDER PHOTOIRRADIATION

Polychloro compounds were added to olefins in the presence of semiconductor particles (TiO2 or CdS) under photoirradiation. The photoreaction without semiconductors afforded no adducts at all; however, loading of TiO2 with Ag, Cu, or Fe3O4 enhanced the yield of the photoaddition reaction even further. Semiconductors operate as catalysts for the one-electron injection into the polychloro compounds. The relative adsorptions of the polychloro compounds onto the semiconductor particles correlate with the yields of the adducts, while the half-wave reduction potentials of the polychlorides do not. This semiconductor-catalyzed reaction was selective to unfunctionalized olefins and to those bearing a functional group at a remote position. An alkyne furnished the product via further reduction following addition, i.e., 1,1,3-trichloro-1-heptene (7) from 1-hexyne and carbon tetrachloride.