Boron Directed RegioselectivAromatic Ortho Functionalizations

Abstract

Selectivity is crucial in modern organic synthesis, as it allows for precise molecular modifications while minimizing undesired side reactions. Controlling selectivity is essential for improving reaction yields, reducing purification steps, and enhancing overall synthetic efficiency. This is particularly important in synthetic methodologies, where precise control over regioselectivity is essential for constructing complex molecules efficiently and reliably. In this work, we have developed a series of selective deborylative transformations that leverage the unique reactivity of dibromoboracycles to achieve regioselective C–halogen, C– aryl, and C–benzyl bond formations in 2–aryl–N–heteroarenes, aldehydes, N–aryl amides and ureas. By integrating nitrogen and carbonyl-directed borylation with subsequent functionalization, we have introduced efficient, metal-free, and scalable methodologies that address long-standing challenges in site-selective C–H functionalization. Our oxidative halodeboronation strategy provides a direct and regioselective approach to ortho-halogenation, eliminating the need for transition-metal catalysts while ensuring high functional group tolerance. This protocol expands the synthetic utility of boron, enabling the precise installation of halogens in 2–aryl–N–heteroarenes and N–aryl amides under mild conditions. Furthermore, we have demonstrated that dibromoboracycles can be directly employed in ortho-arylation and ortho-benzylation, bypassing the conventional BBr₂-to-BPin conversion. This unique approach facilitates the efficient synthesis of biaryl amides, diarylmethane amides, and dibenzoazepines, unlocking new avenues for selective C(sp²)–C(sp²) and C(sp²)– C(sp³) bond formation. Additionally, our method enables one-pot diagonal diarylation, allowing streamlined access to complex molecular architectures such as tetraarylbenzenediamines and N–doped fulminenes. Finally, we introduce a scalable and chromatography-free synthesis of aryl-difluoroborane (Ar–BF₂) compounds, which exhibit enhanced stability and reactivity. These Ar–BF₂ species serve as highly versatile intermediates for late-stage functionalization, enabling diverse transformations, including radioiodination, halogenation, hydroxylation, azidation, and Suzuki-Miyaura cross-coupling. Their broad applicability highlights their potential as powerful tools in pharmaceutical synthesis and beyond. Overall, this work represents a significant advancement in boron-mediated functionalization, establishing a unified platform for regioselective C–H activation and cross-coupling reactions. By harnessing the intrinsic reactivity of dibromoboracycles, we provide highly selective, operationally simple, and scalable strategies that eliminate unnecessary synthetic steps, paving the way for future developments in boron-directed transformations and late-stage functionalization.