10.1021/jacs.9b03328
The research focuses on the regiocontrolled hydrogenation of polycyclic aromatic hydrocarbons (PAHs) using chromium and cobalt catalysis, which is a significant challenge due to the thermodynamic stability of PAHs arising from their aromaticity. The study employs a combination of experimental and theoretical approaches to achieve this hydrogenation at ambient temperature. The reactions are facilitated by the use of inexpensive chromium or cobalt salts, diimino/carbene ligands, and methylmagnesium bromide, leading to high regioselectivity and an expanded substrate scope, including rarely reduced PAHs like tetracene, tetraphene, pentacene, and perylene. The research provides a cost-effective and scalable catalytic protocol for hydrogenation, which can be further utilized in the synthesis of functionalized motifs such as tetrabromo and carboxyl-substituted derivatives. The experiments involve the optimization of reaction conditions, the use of various PAHs as substrates, and the analysis of products through techniques like NMR and GC. Theoretical mechanistic modeling using density functional theory (DFT) was also conducted to understand the active species involved in the hydrogenation process, suggesting that low-valent Cr and Co monohydride species, likely derived from zero-valent transition metals, mediate the hydrogenation of fused PAHs.
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