Halocarbocyclization versus dihalogenation: substituent directed iodine(III) catalyzed halogenations.

The nucleophilicity of the substituents in iodobenzene pre-catalysts have a huge impact on product selectivity in iodine(III) triggered halogenations, steering the reactivity from solely carbocyclizations towards dihalogenations. Utilizing this catalyst-dependent reactivity a diastereo- and chemoselective dihalogenation method was established allowing the conversion of structurally and electronically diverse unsaturated compounds in excellent yields.