Markovnikov-Selective Hydroboration of Aryl Alkenes Catalyzed by Quaternary Ammonium Salts.

The development of catalytic Markovnikov-selective hydroboration of alkenes has seen significant progress; however, achieving this transformation under metal-free conditions has remained a longstanding challenge. Here, we present an organocatalytic method for the Markovnikov-selective hydroboration of aryl alkenes using a readily available quaternary ammonium catalyst. This approach is operationally simple, scalable, and demonstrates broad substrate compatibility. Furthermore, the method enables the efficient synthesis of active pharmaceutical ingredients, including Chlorphenoxamine. Comprehensive experimental and computational studies provide detailed insights into the reaction mechanism and the origins of its regioselectivity, offering a deeper understanding of this transformation.