Cobalt-Salen Catalyzed Hydration of Alkenes with Water: A Complementary Ionic Approach to the Mukaiyama Hydration

Accessing alcohols from readily available chemical feedstocks is a critical process within synthetic methodology. The hydration of olefins is a convenient method for the introduction of an alcohol functional group ideally via the direct addition of water across the alkene. However, current transition metal-catalyzed protocols (Mukaiyama-type hydration) are dominated by radical addition to molecular oxygen. Ionic processes involving direct hydration with water are underexplored, yet highly desirable due to the simplicity of the reagents required. Herein, we report a cobalt-salen catalyzed hydration of alkenes proceeding via a radical–polar crossover mechanism and subsequent nucleophilic attack of water. This is a complementary protocol to previously reported radical-based hydrations which display analogous reactivity to traditional acid-catalyzed methods. The mild reaction conditions employed make the protocol synthetically practical and convenient for accessing alcohols from the corresponding alkenes.