Exploring the Synthesis, Reactivity, and Catalytic Applications of Zinc Boryl Species

Organozinc compounds are versatile intermediates in synthetic chemistry, exhibiting reactivity similar to that of organolithium and Grignard reagents. Traditionally, zinccarbon bonded reagents function as mild carbon-centered nucleophiles; however, recent interest has shifted toward heteroatom-zinc species, which introduce unique reactivity through the Zn-heteroatom bond. Among these, boron, with its vacant 2p orbital in the 3-coordinated state, represents a particularly promising option. Zinc-boryl species can provide access to the nucleophilic reactivity of the boryl moiety, which is challenging to achieve with conventional Lewis-acidic organoboron species. Additionally, zinc serves as an attractive alternative to expensive noble metals, positioning zinc-boryl compounds as promising catalysts for various borylation reactions. Currently, known zinc-boryl species are limited and primarily consist of nitrogenstabilized bulky boryl frameworks, which exhibit constrained reactivity due to steric hindrance. Zinc boryl species derived from diboron(4) reagents (e.g., B₂pin₂ and B₂cat₂) have been proposed as key intermediates in catalytic borylation reactions, yet their synthesis has proven elusive. Our preliminary results demonstrate that stable Zn-B bonds can be achieved through the incorporation of β-diiminate ligands at the Zn centers. Based on this, we have successfully synthesized two examples of Zn-B bonded compounds from B₂pin₂ and B₂cat₂. Notably, the Zn-Bcat species has shown significant reactivity toward unsaturated substrates and holds promise for valuable catalytic applications. Building on these findings, we aim to expand this research by synthesizing a series of zinc-boryl compounds using known diboron reagents. We will explore the reaction chemistry of these new compounds by varying ligands and assessing their reactivity with small molecules and unsaturated substrates. Furthermore, we anticipate that these compounds will exhibit the nucleophilic reactivity of boryl anions, facilitating new boron-element bond formations with various electrophiles. We envision that these zincboryl species will promote catalytic borylation reactions in organic synthesis. This study is expected to yield novel nucleophilic boryl reagents, uncover new reactivity of Zn-B bonds, and develop innovative catalysts for organic synthesis. Our findings will enhance the understanding of main-group compounds, metal boryl species, and their applications in synthetic chemistry.