Photochemistry of irgasan-triflate: A simple conversion of an aromatic hydroxyl group to chlorine in the synthesis of polychlorinated diphenyl ethers and polychlorinated dibenzofurans

Abstract

Several chlorophenoxy phenols were converted to their triflates by reaction with trifluoromethanesulfonyl chloride. The trifilates undergo triplet seneltlzed photolytic cyclizations at 300 nm in acetone to give chlorodibenzofurans or singlet state substitution reactions in carbon tetrachloride saturated with chlorine gas to give the corresponding chlorine substituted diphenyl ethers. 2-Chloro-3-hydroxy dlbenzofuran was similarly converted to the 2,3-dichlorodibenzofuran. The mechanism for displacement of triflate by chlorine appears to involve chlorine-arene π complexation.