Many derivatives of Ru(II) and Ir(III) photocatalysts have been prepared as it is convenient to rapidly and systematically alter the ligand sets with either commercially available or easily prepared ligands to tune the absorption and excited state properties of these molecules. 23, 28, 36 In general, inorganic/organometallic photoredox catalysts offer advantages due to their high molar absorptivities, often efficient intersystem crossing (ISC), and triplet (T 1) lifetimes (~100 ns to 1 ms). The photochemistry and photophysics of inorganic and organometallic photoredox catalysts have been described in detail in a number of articles and reviews. Inorganic/Organometallic Photoredox Catalysts
We have further divided each of these sections to cover both aromatic and aliphatic C–H functionalization reactions and, subsequently, the types of intermediate radical or charged open-shell species that participate in these transformations.ġ.2. We have elected to bifurcate this review into C–H functionalization reactions that employ either inorganic/organometallic or organic photoredox catalysts in order to compare and contrast the reactions possible with each class of catalyst and also to highlight the cases where overlap exists. While there have been numerous reviews and perspective articles on the subject of photoredox catalysis in general, 20– 24, 24– 49 this review will be a comprehensive overview of the use of photoredox catalysis specifically in transformations that involve C–H functionalization. Photoredox catalysis continues to expand at a rapid pace and touches many different fields of scientific inquiry including applications to renewable energy and chemical feedstocks, new reaction development, natural product synthesis, materials and biological applications. 17, 18 Adoption of catalytic C–H functionalization tactics has begun in industry, particularly in pharmaceutical and agrochemical discovery settings. 1– 14 These strategies have been deployed in a number of settings including the selective functionalization of natural products, 7, 15 late-stage functionalization of pharmaceutical derivatives, 16 petroleum feedstocks and polymers. Catalytic strategies involving transition metals, enzymatic systems, photochemical, electrochemical and photoredox systems have all been utilized for the selective functionalization of C–H bonds. The field of catalytic C–H functionalization has continued to grow at a rapid pace over the past four decades both in terms of the scope of transformations that are possible as well as the types of catalytic manifolds that enable C–H functionalization.
0 kommentar(er)
