Recent advances in transition metal-asymmetric carbene B–H insertion reactions provide a straightforward and powerful protocol to access chiral organoboron compounds. However, the related reaction involving linear alkyl carbenes has not been successfully developed. Apart from the difficulty of controlling the enantioselectivity, another major challenge is the high propensity of the alkyl metal carbene to undergo a β-hydride migration to form undesired alkenes. Herein, we report our development of an efficient alkyl carbene B–H insertion reaction using rhodium(I)/diene complexes as the catalysts. This simple catalytic system not only reduces the formation of alkene byproduct but also achieves high enantioselectivity of the carbene B–H insertion. This method facilitates easy asymmetric access to a wide variety of structurally diverse alkylboranes in high yields, and their further synthetic application and transformation have also been described. Mechanistic studies show that the β-hydride migration is less favorable than the carbene insertion pathway under the rhodium(I)/diene catalytic system and that the B–H bond insertion is the rate-limiting step.
Organic electrode materials for lithium-ion batteries (LIBs) have attracted increasing attention due to their potential low cost and renewability. Although oxygen atoms have been the most common redox-active sites of n-type organic electrode materials, it is a great challenge to develop high-performance oxygen-based p-type materials. In this study, we designed and synthesized two organic cathode materials with benzofuran (BF) as the active unit. Connecting two BF units onto para-positions of benzene or pyrazine increased the molecular size and maintained the planar structure, which facilitated enhanced intermolecular interaction, and thus, reduced solubility. Importantly, we found that the target molecules could undergo in situ electropolymerization during the charging process inside the batteries, which further reduced the solubility and stabilized the electrode structure. Electrochemical tests showed that the optimized cathode materials could reach 99.5% of theoretical capacity in LIBs, with a high capacity of up to 170.9 mAh g−1. In addition, they could be stably cycled 5,000 times with a high capacity retention of 75.1%, which corresponded to an average capacity loss of only 0.005% per cycle. These exciting results should arouse much interest in the study of p-type organic cathode materials with oxygen atoms as active sites.
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