Indium Catalyzed Hydrofunctionalization of Styrene Derivatives Bearing a Hydroxy Group with Organosilicon Nucleophiles

Hydrofunctionalization is one of the most important transformation reactions of alkenes. Herein, we describe the development of an indium-triiodide-catalyzed hydrofunctionalization of alkenes bearing a hydroxy group using various types of organosilicon nucleophiles. Indium triiodide was the most effective catalyst, whereas typical Lewis acids such as TiCl₄, AlCl₃, and BF₃·OEt₂ were ineffective. Many functional groups were successfully introduced, and these resulted in yields of 31–86%. Various styrene derivatives were also applicable to this reaction. Mechanistic investigation revealed that the present hydrofunctionalization proceeded through Brønsted acid-catalyzed intramolecular hydroalkoxylation of alkenes followed by InI₃-catalyzed substitution reaction of cyclic ether intermediates.