A significant breakthrough has been achieved by a research team led by Prof. Dai Wen from the Dalian Institute of Chemical Physics (DICP) under the Chinese Academy of Sciences (CAS) in the field of borylation reactions utilizing N-heterocyclic carbene boranes (NHC-BH3). This innovative approach harnesses a straightforward yet remarkably efficient heterogeneous photocatalytic system, ushering in the potential for transformative outcomes like hydroboration and boron substitution products. The monumental findings were recently published on August 9th in the prestigious journal Angewandte Chemie International Edition.
NHC-BH3 presents a promising avenue as a novel boron source in free radical borylation reactions due to its inherent stability and uncomplicated preparation procedure. Despite its potential, the practical application of NHC-BH3 has been impeded by the need for substantial quantities of harmful free radical initiators, alongside the financial implications and non-reusability associated with homogeneous photocatalysts.
In this study, the research team ingeniously employed cadmium sulfide nanosheets, conveniently synthesized, to serve as heterogeneous photocatalysts. Concurrently, NHC-BH3 was harnessed as a boron source, effectively enabling precise borylation reactions across a spectrum of compounds encompassing alkenes, alkynes, imines, aromatic (hetero) rings, and bioactive molecules. Impressively, these reactions were conducted at room temperature and under the influence of light. Leveragingphotogenerated electron-hole pairs negated the necessity for sacrificial agents.
Furthermore, the researchers made a pivotal discovery—their photocatalytic system not only facilitated substantial gram-scale amplification but also maintained a consistent yield across multiple cycles of catalyst usage. Moreover, this catalytic system demonstrated an eco-friendly facet, with the rejuvenated catalyst demonstrating seamless catalytic capabilities across diverse substrates.
Prof. Dai underlined the significance, stating, “Our study introduces pioneering paradigms for advancing free radical borylation reactions through the utilization of NHC-BH3 as a potent boron source. The resultant organoboranes from these reactions possess the potential to form the bedrock for synthesizing compounds housing reactive sites like hydroxyl, borate, and difluoroborane.”
This remarkable stride represents a pivotal juncture in the realm of borylation reactions, offering a sustainable and profound methodology for the synthesis of intricate compounds that hold versatile and wide-ranging applications.
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