Markovnikov Selective Hydroboration of Aryl Alkenes Catalyzed by Quaternary Ammonium Salts

Despite recent advancements in the development of catalytic Markovnikov-selective hydroboration of alkenes, the metal-free procedure has long remained an unsolved challenge. Here, we report an organocatalytic Markovnikov-selective hy-droboration of aryl alkenes using a commercially available quaternary ammonium catalyst. The method is operationally simple, scalable, and compatible with a wide variety of substrates and it can be successfully applied in the synthesis of active pharmaceutical ingredients (API) such as Chlorphenoxamine. Through in-depth experimental and DFT studies, we elucidate a nuanced understanding of the mechanism and regioselectivity of this reaction.