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.
Addition of Trichloromethyl Radicals to Alkenes: The Use of Phosphites as Hydrogen-Atom Donors in Intermolecular Radical Reactions
作者:Jenny M. Barks、Bruce C. Gilbert、Andrew F. Parsons、Bala Upeandran
DOI:10.1055/s-2001-18086
日期:——
Addition of trichloromethyl radicals (generated from BrCCl3 or CCl4) to a variety of alkenes in the presence of hydrogen-atom donors has been explored. The use of phosphites as hydrogen-atom donors was shown to provide a mild, novel and technically clean approach to trichloroalkanes.