Manganese-catalyzed chemodivergent transfer hydrogenation of unsaturated esters switched by solvent

Abstract

We report a solvent-switchable chemodivergent transfer hydrogenation of α,β-unsaturated esters, employing an Earth-abundant manganese complex as the catalyst and ammonia borane as the hydrogen donor. Diverse unsaturated esters are efficiently converted into saturated esters in dioxane and primary alcohols in MTBE. Mechanistic investigations demonstrate that the manganese hydride species formed in MTBE exhibit superior reactivity to those formed in dioxane, establishing a practical protocol for this chemodivergent reduction. Gram-scale transfer hydrogenation of ethyl cinnamate validates the methodology, affording the saturated ester in 91.2% yield and the primary alcohol in 80% yield under the respective conditions.